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c6a2f32f-97f2-4239-bee5-5d2f4fdc6792
| 5 |
The fluorescence emission of the product of the reaction of papain with compound (I) was shown to be 25 times more intense than that of the product of the reaction of papain with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (Nbd chloride). 7. The second-order rate constants (k2) for the reactions of compound (I) and of Nbd chloride with GSH, papain, albumin, ficin, 2-benzimidazolylmethanethiol and 2-benzimidazolylethanethiol were determined at 25.0
|
c6a2f32f-97f2-4239-bee5-5d2f4fdc6792
| 6 |
degrees C and various pH values. At pH4 the values of k2(compound I)/k2(Nbd chloride) are: GSH, 288; albumin, 36; papain 3 X 10(3); ficin, 3 X 10(4). 8. The pH-k2 profiles for the reactions of compound (I) and of Nbd chloride with the two 2-benzimidazolylalkanethiols were determined.
|
c6a2f32f-97f2-4239-bee5-5d2f4fdc6792
| 7 |
Of the four profiles only that for the reaction of compound (I) with 2-benzimidazolylmethanethiol is characterized by a striking rate maximum in acidic media.
|
3bc2f72e-89a0-4121-bc61-75b4c1239947
| 0 |
Differential effects of temperature on a membrane adenosine triphosphatase and associated phosphatase. Arrhenius plots of a membrane (Na+ + K+)-dependent ATPase (adenosine triphosphatase) activity showed characteristic discontinuities, whereas those of the associated K+-dependent phosphatase activity did not. These findings support the contention that the phosphatase activity does not depend on phospholipid in the same way as does the ATPase activity.
|
4969a130-5303-45dd-bf40-eca7048613d7
| 0 |
The action of chelating agents on human liver aldehyde dehydrogenase. Human liver aldehyde dehydrogenase was inhibited by aromatic chelating agents. However, structurally related compounds with much lower metal-complexing ability displayed affinities for enzyme essentially equal to those of their respective chelating analogues. Inhibition was competitive with respect to the coenzyme. It is suggested that hydrophobic interactions between the inhibitors and the coenzyme-binding site of the enzyme are responsible for the observed effects on activity.
|
d63c859f-e2e4-40ab-b822-9d3356f72f03
| 0 |
An improved assay for bacterial methane mono-oxygenase: some properties of the enzyme from Methylomonas methanica. Extracts of Methylomonas methanica catalyse the O2-and NAD(P)H-dependent disappearance of bromomethane. The activity is unstable at 2 degrees C but is stable at --70 degrees C for several weeks. Bromomethane mono-oxygenase is particulate and is inhibited by metal-binding reagents, by compounds SKF 525A and Lilly 53325, by some metal ions and by acetylene. Evidence is presented that indicates that bromomethane mono-oxygenase is the enzyme responsible for methane oxidation in vivo.
|
2448276a-7fbc-46dc-90a7-715133edd771
| 0 |
Iron oxidation and transferrin formation by phosvitin. The catalytic activity of phosvitin in Fe(II) oxidation and the addition of iron to transferrin were studied under various conditions. It was concluded that the Fe(II) oxidized by phosvitin would bind to apotransferrin, although an appreciable fraction of Fe(III) remained bound to phosvitin.
|
2448276a-7fbc-46dc-90a7-715133edd771
| 1 |
Fe(III) also migrated from phosvitin to apotransferrin. This reaction was first-order with respect to Fe(III)-phosvitin concentration with a half-time (t1/2) of 10 min, and a first-order rate constant, k=0.069min-1, in 700 muM-phosphate buffer, pH 7.2, at 30 degrees C.
|
2448276a-7fbc-46dc-90a7-715133edd771
| 2 |
The catalysis of the oxidation of Fe(III) by phosvitin was proportional to O2 concentration, and is quite different from the relative O2 independence of Fe(II) oxidation as catalysed by ferroxidase. A scheme for the mobilization and transfer of iron in the chicken, including the role of ferroxidase, phosyitin and transferrin, is presented.
|
29898cfc-313a-4300-8b0c-53eb5ea18cbe
| 0 |
The substrate specificity of thermomycolase, an extracellular serine proteinase from the thermophilic fungus Malbranchea pulchella var. sulfurea. The specificity of thermomycolase toward glucagon and the oxidized A and B chains of insulin was investigated. Extensive digestion of glucagon occurred when conducted at pH 7.0 and 45 degrees C for 40 min, whereas hydrolysis of only three peptide bonds occurred at pH 7.0
|
29898cfc-313a-4300-8b0c-53eb5ea18cbe
| 1 |
and 28 degrees C for 5 min. A similar situation was observed for the oxidized B chain of insulin, which exhibited only a single major cleavage after 5 min at 25 degrees C. No well-defined specificity for particular amino acid residues was evident, but ready hydrolysis of peptide bonds occurred within sequences containing non-polar residues.
|
29898cfc-313a-4300-8b0c-53eb5ea18cbe
| 2 |
This endoproteinase must therefore possess an extended hydrophobic binding site for polypeptides. Thermomycolase hydrolysed acetylalanylalanylalanine methyl ester and elastin-Congo Red at 22 and 8.5 times the rate of porcine elastase respectively. A limited degradation of native collagen and significant hydrolysis of benzyloxycarbonyl-Gly-Pro-Leu-Gly-Pro were suggestive of some collagenase-like activity.
|
29898cfc-313a-4300-8b0c-53eb5ea18cbe
| 3 |
No keratinase activity was apparent.
|
5514743b-2df5-4950-94fd-ab7c1b4ff972
| 0 |
Stimulation of rat liver beta-galactosidase activity by ions. 1. The p-nitrophenyl beta-D-galactosidase asctivity in rat liver homogenates of lysosome-rich fractions was shown to be markedly affected by the ionic composition of the medium. A stimulation of the reaction rate at pH 5 was produced by most of the salts tested, which contained anions such as acetate, SO4(2-) and Cl-, and cations such as Na+, K= and Mg2+.
|
5514743b-2df5-4950-94fd-ab7c1b4ff972
| 1 |
The most pronounced effect was observed with MgCl2. Only potassium glutamate was inhibitory. 2. Five peaks of beta-galactosidase activity obtained by DEAE-cellulose chromatography were equally sensitive to changes in the ionic composition of the medium. In the presence of added NaC1, the whole rate-pH curve was displaced towards higher pH values, the optimum being shifted from 2.0
|
5514743b-2df5-4950-94fd-ab7c1b4ff972
| 2 |
-2.5 to 3.5. The stimulation at pH 5.0 appeared to be mainly due to changes in Vmax., whereas the apparent Km was slightly modified. 3. Unlike the total, the free beta-galactosidase activity remained unchanged or even declined when KC1 was added to the reaction medium.
|
44e3cc46-659e-461e-bdab-a02d7cd125bc
| 0 |
Pig heart lactate dehydrogenase. Binding of pyruvate and the interconversion of pyruvate-containing ternary complexes. 1. Lactate oxidation catalysed by pig heart lactate dehydrogenase was studied in the presence of inhibitory concentrations of pyruvate. Experimental results show the presence of an intermediate which occurs immediately after the hydride transfer step, but before the dissociation of pyruvate and the H+ produced by the reaction.
|
44e3cc46-659e-461e-bdab-a02d7cd125bc
| 1 |
The rate constant for pyruvate dissociation and the dissociation constant for pyruvate from the ternary complex differ from those obtained in pyruvate reduction experiments. 2. In single-turnover pyruvate reduction by pig heart lactate dehydrogenase at pH8.0 pyruvate can bind to the enzyme before a H+ is taken up, and the subsequent uptake of a H+ is governed by a step that is also rate-limiting for single-turnover and steady-state NADH oxidation.
|
44e3cc46-659e-461e-bdab-a02d7cd125bc
| 2 |
3. Observation of various intermediates in the single-turnover pyruvate reduction experiments has made it possible to determine separately the dissociation constant and Km value for pyruvate at pH8.0, and also the catalytic turnover rate and Km for pyruvate under first-order conditions at different pH values. 4.
|
44e3cc46-659e-461e-bdab-a02d7cd125bc
| 3 |
Further studies on single-turnover pyruvate reduction carried out in 2H2O, or in water at low temperature, show another step which, under these conditions, is slower than that controlling H+ uptake and rate-limiting for NADH oxidation. A scheme is presented which explains these results.
|
d79a6069-59bc-4cd2-b3f3-a76975134899
| 0 |
[Analytical profile of purified hexetidine (author's transl)]. Physico-chemical, spectroscopic (UV, IR, NMR, mass), chromatographic (GLC, TLC) properties and synthesis of 1,3-bis(2-ethylhexyl)-5-amino-5-methyl-hexahydropyrimidine (hexetidine) are reported and discussed. Moreover, the difference between commercial and purified hexetidine is demonstrated.
|
b5e7f6ce-55eb-4420-81dc-f8602c0faf97
| 0 |
[Ditertiary diamine compounds (author's transl)]. The preparation of ditertiary aliphatic diamines 3 designed as drugs protecting CNS acetylcholinesterase against organophosphate inhibition, is described. Owing to the radicals at the basic nitrogen atoms, these compounds should exist in appreciable amounts both as base and as diammonium ion at biological pH's.
|
0c57e42d-ad48-400a-87ca-bd70fd150d3d
| 0 |
[Intracellular pH of cardiac muscle after administration of potassium-magnesium-aspartate (author's transl)]. 27 Sprague-Dawley rats were anesthetized with pentobarbital. Artificial ventilation was given by a Starling pump respirator via a tracheal tube. Intracellular pH of cardiac muscle was determined by means of the indirect procedure of measuring the distribution of 5,5-dimethyl-2,4-oxazolidinedione (DMO) in intra- and extracellular spaces (DMO-method).
|
0c57e42d-ad48-400a-87ca-bd70fd150d3d
| 1 |
12 rats were injected i.p. with 0.33 mval potassium-magnesium-aspartate/100 g body weight and 15 rats served as controls. Using a regression analysis, the following relationships were obtained: 1. animals injected with potassium-magnesium-aspartate pHa = --0.75 log PaCO2 + 8.535, PHi = --0.30
|
0c57e42d-ad48-400a-87ca-bd70fd150d3d
| 2 |
log PaCO2 + 7.509, pHi = 0.41 pHa + 4.036; 2. control animals pHa = --0.59 log PaCO2 + 8.308, pHi = --0.27 log PaCO2 + 7.381, pHi = 0.47 pHa + 3.503. At a pCO2 of 40 torr a pHa of 7.33 (7.36) and a pHi of 7.03
|
0c57e42d-ad48-400a-87ca-bd70fd150d3d
| 3 |
(6.95) was obtained. At an arterial pH of 7.40 the pHi was 7.07 (6.98). The results of the control group are written in brackets. -- The experiments demonstrate an increase in the intracellular buffer bases after administration of potassium-magnesium-aspartate. This effect can be recognized by a concomitant increase in the intracellular pH of 0.09
|
0c57e42d-ad48-400a-87ca-bd70fd150d3d
| 4 |
compared to the control group.
|
fce2566b-378a-476e-a51a-7b541b60fa49
| 0 |
Pharmacological properties of 2-(2-chloro-p-toluidino)-2-imidazoline-nitrate (tolonidine), a new antihypertensive agent. III. Action on the secretions of the digestive tract and on the central nervous system, acute toxicity. The pharmacological properties of 2-(2-chloro-p-toluidino)-2-imidazoline-nitrate (tolonidine) a new synthetic derivative of imidazoline are reported in a series of three successive articles.
|
fce2566b-378a-476e-a51a-7b541b60fa49
| 1 |
This compound has been shown to possess hypotensive and antihypertensive properties. After i.v. administration, the hypotensive phase was preceded by hypertension related to the potent direct alpha-sympatheticomimetic properties of the product. This pressor response, which was not seen after oral administration, was accompanied by a marked decrease in cardiac output and a significant increase in peripheral vascular resistance.
|
fce2566b-378a-476e-a51a-7b541b60fa49
| 2 |
The hypotensive action of the product was due to a drop in cardiac output probably reinforced by a decrease in vasoconstrictor sympathetic tone due to a central action. Whatever the route of administration, tolonidine slowed heart rate independently of blood pressure variations, due essentially to an increase in vagal tone.
|
fce2566b-378a-476e-a51a-7b541b60fa49
| 3 |
In studies of diuresis, liquid and salt loss were observed in the cat, not in the dog. At doses which induce a drop in blood pressure tolonidine did not produce a reduction in pilocarpine-induced salivary secretion and only partially inhibited gastric secretion. In the central nervous system, tolonidine produced a sedation which first appeared at doses having an antihypertensive effect but which was only fully apparent with increased doses.
|
fce2566b-378a-476e-a51a-7b541b60fa49
| 4 |
A decrease in the release of cerebral amines, serotonin and noradrenaline by tolonidine is proposed. Tolonidine was compared with three other antihypertensive agents: clonidine, which is structurally related, and guanethidine and mecamylamine, which are structurally unrelated and have a different mode of action. A close resemblance of the pharmacological properties of tolonidine and clonidine was established due to the chemical relationship between the two substances.
|
ba8d80f0-64b3-4fa3-9a07-926539690f64
| 0 |
[On the influence of a special preparation of oxytetracycline and sodiumbituminosulfonates on amount and composition of skin surface lipids in acne vulgaris (author's transl)]. Two groups of 27 and 23 patients with acne vulgaris were first treated for a period of one week with 1 g oxytetracycline a day p.
|
ba8d80f0-64b3-4fa3-9a07-926539690f64
| 1 |
o. In a second treatment period of 6 weeks the first group received 100 mg oxytetracycline a day p.o. and the second group a combination of 100 mg oxytetracycline and 1.2 g sodiumbituminosulfonates a day p.o. In the third treatment period, similarly continued for 6 weeks, the method was reversed.
|
ba8d80f0-64b3-4fa3-9a07-926539690f64
| 2 |
Gastric juice-insoluble preparations were used for the investigation. All criteria for a double-blind study were considered. Amount and composition of the skin surface lipids were analysed before beginning the treatment, at the end of the 2nd and at the end of the 3rd treatment period. The combination of both agents in gastric juice-insoluble preparations suppresses to a great extent the known effects brought about by the substances separately, namely the reduction in free fatty acids and the decrease in the skin surface lipids.
|
ba8d80f0-64b3-4fa3-9a07-926539690f64
| 3 |
The findings also show that the reduction of the free fatty acids was in a limited time observed only in patients treated with 100 mg oxytetracycline a day p.o. if they had been treated in the beginning of this therapy with a higher dosage of tetracycline.
|
b554b42f-3ab7-4a74-8a83-d8c4f22f8af6
| 0 |
[Influence of ethanol on the in vitro and in vivo drug release from some sustained release tablets (author's transl)]. The in vitro and in vivo liberation of acetylsalicylic acid from sustained release tablets in presence of ethanol is described. Simultaneous uptake of 120 ml commercial brandy resulted in a faster release of the active substance from the tablets prepared with Eudragit ret-l (PM), as has been proved by urinary excretion data. These results were supported by experiments with a pH-endoaradio transmitter and by radiography.
|
49ade883-0dd0-4d98-93ec-ca26cfc54499
| 0 |
Changes in liver function after different types of surgery. Liver function tests carried out after minor surgical procedures, under anaesthesia lasting for 1 hr, showed no abnormalities. Tests after body surface operations under the same anaesthetic techniques showed transient derangements. After intra-abdominal procedures, liver dysfunction was more marked, although no patients with evidence of preoperative liver dysfunction or postoperative surgical complications were studied and none received blood transfusions.
|
49ade883-0dd0-4d98-93ec-ca26cfc54499
| 1 |
Measurements of the serum bilirubin concentration showed the most frequent abnormalities, but the pseudocholinesterase concentration decreased progressively after intra-abdominal surgery and b.s.p. retention increased significantly. Serum concentration of intracellular enzymes (LDH, s.g.o.t. and s.g.p.t.) increased within an hour of starting surgery, changes which were probably not related to liver function.
|
896d7409-8826-49b4-8109-26d574edc16c
| 0 |
Studies on the energy metabolism in lichen planus. Various epidermal enzymes and cofactors were measured in patients with lichen planus and in healthy controls with the aid of Lowry's microtechniques, including enzymatic cycling. The steady-state levels of the nicotinamide adenine dinucleotides NAD and NADP were decreased and this was evident even in areas still free from lesions.
|
896d7409-8826-49b4-8109-26d574edc16c
| 1 |
The oxidized and reduced portions of NAD were altered indicating changed equilibria of NAD dependent dehydrogenases. Reduced NADP was more tightly controlled at the normal level which is regarded as evidence of an unaltered biosynthetic potential in this disease. In conjunction with earlier data the results indicate a preserved glycolytic and pentose shunt activity while the mitochondria display signs of dysfunction.
|
65c3f28e-65fe-43aa-ae70-09aa40aa6258
| 0 |
The lichen planus-like eruption after bone marrow transplantation. A lichen planus-like eruption was seen in four patients after bone marrow transplantation. The skin and mucous membrane appearance closely mimicked lichen planus. The histopathology was also very similar to lichen planus. The occurrence of a lichen planus-like eruption (LPLE) after an immune basal cell damage related to the graft-versus-host reaction raised the question of the immune nature of this eruption.
|
65c3f28e-65fe-43aa-ae70-09aa40aa6258
| 1 |
The correlation found between biological signs of graft-versus-host reaction and the out-break or relapse of the lichen planus-like eruption supports the hypothesis that the skin changes could be a sign of a chronic immune response against recipient epidermis.
|
79d0cfbe-334f-41c7-8251-e1de367c55f0
| 0 |
The effect of pH upon human transferrin: selective labelling of the two iron-binding sites. The influence of pH changes upon the iron-binding properties of transferrin was investigated in the absence of chelating agents. The effects were demonstrated by spectrophotometry, gel filtration, and by studies of the intermolecular transfer of 59Fe from transferrin to conalbumin.
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79d0cfbe-334f-41c7-8251-e1de367c55f0
| 1 |
At pH values below 6.7, diferric transferrin readily loses iron. The monoferric molecule, which is relatively resistant to acid dissociation, is preferentially formed. A temporary reduction of pH provides a simple method for selectively attaching iron to one metal-binding site, and allows double isotopic labelling of the transferrin molecule.
|
79d0cfbe-334f-41c7-8251-e1de367c55f0
| 2 |
This technique may permit further investigation of the physiological properties of the two iron-binding sites.
|
2aa443b2-ceb2-41e2-8511-5ecbc1a71291
| 0 |
The effect of parturition on amniotic fluid lecithin concentration. Amniotic fluid lecithin has been measured during the antenatal period and at comparable periods of gestation at the onset of spontaneous labour. Lecithin values were higher in labour, the difference being statistically significant in two of the three groups studied. Lecithin values were also measured serially during induced labour in 14 normal women at term. A significant fall was observed throughout labour. Creatinine levels were measured in the amniotic fluid in five of these patients and showed no significant change.
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ed9bf99c-6986-43f9-8a81-6fcf7f862512
| 0 |
The effects of narcotics on fetal acid base status. This paper reports two randomized control trials on the effects of nalorphine, pethidine, morphine and heroin on fetal and maternal acid base status. The drugs decreased pH and increased pCO2 in the mother, and decreased pH and base excess in the fetus.
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ed9bf99c-6986-43f9-8a81-6fcf7f862512
| 1 |
The changes in the fetus were independent of the changes in the mother. In equivalent dosages, nalorphine increased maternal pCO2 more than pethidine and morphine. The effects of heroin were found to be greater than that of other drugs, and we suggest that heroin should be avoided where the fetus is already at risk.
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47e80773-f937-432a-b76d-fa3048d4cc99
| 0 |
On the solution conformation of bradykinin and certain fragments. A circular dichroism (CD) study of [D-Pro2]- and [D-Pro3]-bradykinin, selected peptide fragments, and the model compound. N-acetyl-L-phenylalaninamide, support our previous conclusion (Biochemistry 12, 3780, 1973) that the positive 221-nm CD band of bradykinin is a composite of bands due to two chromophores, the 217-nm band characteristic of the Phe residues overlying the 223-nm band of the N-terminal sequence, Arg-Pro-Pro.
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47e80773-f937-432a-b76d-fa3048d4cc99
| 1 |
The results also indicate that the 223-nm band of Arg-Pro-Pro is associated with the configuration of the Pro-Pro sequence, Arg-D-Pro-Pro and Arg-Pro-D-Pro virtually being diastereoisomers. Accordingly, the conformation of Arg-Pro-Pro was probed in further detail.
|
47e80773-f937-432a-b76d-fa3048d4cc99
| 2 |
Upon increasing the temperature from about 27 to 65 degrees C, Arg-Pro-Pro undergoes a conformational transition characterized by large positive values of deltaHdegrees and deltaSdegrees, which is interpreted to mean that the structure of water and, thus, solute-solvent interactions play a dominant role in determining the conformation of the peptide 13C nuclear magnetic resonance spectroscopy indicates that the effect of lowering the pH on the CD of Arg-Pro-Pro is explicable in terms of hydrogen-bond formation between the carboxyl group and Pro2 carbonyl oxygen at acid pH with concomitant cis to trans isomerization.
|
c39c0ca7-d974-4003-ae77-c5cd34c226dd
| 0 |
The activation of ribulose-1,5-bisphosphate carboxylase by carbon dioxide and magnesium ions. Equilibria, kinetics, a suggested mechanism, and physiological implications. Ribulose-1,5-bisphosphate carboxylase was activated by incubation with CO2 and Mg2++, and inactivated upon removal of CO2 and Mg2+ by gel filtration.
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c39c0ca7-d974-4003-ae77-c5cd34c226dd
| 1 |
The activation process involved CO2 rather than HCO3-. The activity of the enzyme was dependent upon the preincubation concentrations of CO2 and Mg2+ and upon the preincubation pH, indicating that activation involved the reversible formation of an equilibrium complex of enzyme-CO2-Mg. The initial rate of activation was linearly dependent upon the CO2 concentration but independent of the Mg2+ concentration.
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c39c0ca7-d974-4003-ae77-c5cd34c226dd
| 2 |
Kinetic analyses indicated that the enzyme reacted first with CO2 in a rate-determining and reversible step, followed by a rapid reaction with Mg2+ to form an active ternary complex (see eq 1 in text). The pseudo-first order rate constant, kobsd, for the activation process at constant pH was derived:
|
c39c0ca7-d974-4003-ae77-c5cd34c226dd
| 3 |
kobsd=k1[CO2] + (k2k4/k3[Mg2+]). Experimentally, kobsd was shown to be linearly dependent upon the CO2 concentration and inversely dependent upon the Mg2+ concentration. The activity of the enzyme after preincubation to equilibrium at constant concentrations of CO2 and Mg2+ increased as the preincubation pH was raised, indicating that CO2 reacted with an enzyme group whose pK was distinctly alkaline.
|
c39c0ca7-d974-4003-ae77-c5cd34c226dd
| 4 |
It is proposed that the activation of ribulose-1, 5-biphosphate carboxylane involves the formation of a carbamate.
|
6091e0d8-fde8-413c-9d58-86b649d092ed
| 0 |
Manganese (II) and substrate interaction with unadenylylated glutamine synthetase (Escherichia coli w). II. Electron paramagnetic resonance and nuclear magnetic resonance studies of enzyme-bound manganese(II) with substrates and a potential transition-state analogue, methionine sulfoximine. The enhancement of the longitudinal proton relaxation rate of solvent water protons which occurs when Mn(II) is bound to the "tight" metal ion site of unadenylylated glutamine synthetase (GS) was used to determine the binding constant of L-methionine (SR)-sulfoximine to GS-Mn(II) complexes.
|
6091e0d8-fde8-413c-9d58-86b649d092ed
| 1 |
The binary enhancement for GS-Mn(II) is 22 at 24 MHz, 25 degrees C. The enhancement is lowered in the presence of the sulfoximine and the computed dissociation constant is 30 muM with epsilont, the enhancement for the ternary complex, equal to 3.0. Titration curves for the sulfoximine were also obtained in the presence of Mg-ADP, Mg-ADP plus Pi, and Mg-ATP.
|
6091e0d8-fde8-413c-9d58-86b649d092ed
| 2 |
The dissociation constants were 9, 5, and 0.8 muM, respectively. The progressive tightening of the dissociation constants is symptomatic of conformational changes at the active site as the total subsite occupied by ATP is filled. The number of rapidly exchanging water molecules drops from 2 to approximately 0.1
|
6091e0d8-fde8-413c-9d58-86b649d092ed
| 3 |
when saturating concentrations of L-methionine (SR)-sulfoximine and nucleotide are present. The kinetically determined KI value of approximately 4 muM for the sulfoximine is about three orders of magnitude tighter than thee Km' value of approximately 3 mM for L-glutamate. The previously mentioned dissociation constants obtained by enhancement titrations are also orders of magnitude tighter than Km'.
|
6091e0d8-fde8-413c-9d58-86b649d092ed
| 4 |
These data suggest that L-methionine (SR)-sulfoximine is a "transition-state" analogue for the glutamine synthetase reaction. ...
|
3552d5a1-2e2e-4af0-80fb-e3833dd3ebdb
| 0 |
The interaction of borate and sulfite with pyridine nucleotides. The kinetics and equilibria of the borate interaction at ribose with NAD+ and NMN+ have been measured using as a chromophoric probe the perturbation effect borate has on the addition of sulfite to the 4 position of the nicotinamide ring.
|
3552d5a1-2e2e-4af0-80fb-e3833dd3ebdb
| 1 |
NAD+ and NMN+ have more favorable borate association constants than do their corresponding sulfite addition complexes. The rate of interaction of the ribose moiety with borate at low borate buffer concentration is dependent on the concentration of both borate and boric acid.
|
3552d5a1-2e2e-4af0-80fb-e3833dd3ebdb
| 2 |
At high borate concentration the rate becomes independent of borate concentration, indicating the existence of a two-step process for the interaction of NAD-sulfite with borate with a change of rate-determining step from the interaction of the ribose hydroxyl group with borate at low borate to an elimination of sulfite at high borate concentration. A linear free energy relationship with a slope of 0.94
|
3552d5a1-2e2e-4af0-80fb-e3833dd3ebdb
| 3 |
describes an increased reactivity of the nucleotide for sulfite as the affinity of the nucleotide for sulfite increases.
|
17c868c3-dd7e-41d3-b5a2-8c36edd8d6eb
| 0 |
Oxidation of corticosteroids to steroidal-21-oic acids by human liver enzyme. An enzyme that oxidizes corticosteroids to acidic metabolites has been purified from postmortem human liver. The most rapidly oxidized substrate was 11-deoxycorticosterone (DOC). Other corticosteroids were oxidized at rates that were 10% or less of DOC.
|
17c868c3-dd7e-41d3-b5a2-8c36edd8d6eb
| 1 |
The products of DOC oxidation were 3, 20-dioxopregn-4-en-21-oic acid and 20-hydroxy-3-oxopregn-4-en-21-oic acid. The 20-keto acid was the predominant metabolite in all enzyme preparations. Keto acid and hydroxy acid were not interconverted. Enzyme activity was assayed by measuring the transfer of tritium from [21-3H]DOC to water.
|
17c868c3-dd7e-41d3-b5a2-8c36edd8d6eb
| 2 |
The enzyme is yellow, and has spectral maxima at 278 and 405 nm. Inhibition by o-phenanthroline suggests that it may be a metalloenzyme. Molecular weight was estimated at 74 000 +/- 8 000; a pH maximum occurred at pH 8-8.5. This enzyme may participate in the in vivo conversion of corticosteroids to the acidic metabolites that we have described previously (H.
|
17c868c3-dd7e-41d3-b5a2-8c36edd8d6eb
| 3 |
L. Bradlow et al. (1973), J. Clin. Endocrinol. Metab. 37, 811).
|
5e6a8871-254b-43b8-868c-21e1ffaa45ae
| 0 |
A spectrophotometric and fluorimetric study of alkaline transitions of Euglena cytochrome c 552. The behavior of the photosynthetic cytochrome c552 upon titration with alkali depends on the ionic composition of the medium. In water the disappearance of the 695-nm band, indicating the displacement of the methionine ligand, as well as a remarkable tryptophan fluorescense enhancement, follow a single proton titration curve with pK of 10.0
|
5e6a8871-254b-43b8-868c-21e1ffaa45ae
| 1 |
and n=1.0. The product is a low spin type protein. In salt-containing media two successive steps are observed: in the first one, completed at about pH 10.3, a high-spin form of cytochrome c 552 is obtained and relatively small fluorescence enhancement is detected. In the second step, more profound fluorometric changes occur, while the material reverts to its low-spin form.
|
5e6a8871-254b-43b8-868c-21e1ffaa45ae
| 2 |
Addition of salts to an alkaline solution of cytochrome c 552 in water results in the formation of a 600-nm high-spin band with a concomitant quenching of tryptophan fluorescence. The results imply that at high pH unfolding of the molecule is evident only when the low-spin product is obtained.
|
5e6a8871-254b-43b8-868c-21e1ffaa45ae
| 3 |
In the high-spin alkaline form, the methionine ligand is probably displaced from iron coordination by hydroxyl ions, while in the low-spin alkaline form methionine may be replaced by a lysyl residue of the cytochrome c 552 protein. The results imply that the lysyl residue is available for coordination in salt solutions at a higher pH than in water.
|
0f5b3888-e234-4968-94da-71ba267c523a
| 0 |
Synthetic flavinyl peptides related to the active site of mitochondrial monoamine oxidase II. Fluorescence properties. The fluorescence properties of various 8alpha-sulfur-linked flavinyl peptides and related flavin analogues were investigated as the pH solvent, temperature, and flavin concentration were varied. Substitution in the 8alpha position by a thioether-linked peptide brings about a marked quenching of fluorescence (up to 98% in water), a slight bathochromic shift and broadening of the fluorescence emission spectra, and a slight decrease in the fluorescence lifetimes.
|
0f5b3888-e234-4968-94da-71ba267c523a
| 1 |
Oxidation of the thioether function to a sulfone partially releases this fluorescence quenching without further changes in the fluorescence emission spectra. The primary effect on the fluorescence intensity is due to an interaction between the nonbonding electrons of the thioether, the hydrogen-bonding, polar solvent, and the isoalloxazine ring.
|
0f5b3888-e234-4968-94da-71ba267c523a
| 2 |
Dissolving these flavinyl peptides in nonaqueous solvents increases the fluorescence intensity as much as 20-fold. A secondary effect on flavinyl fluorescence can be attributed to a collisional quenching by the vicinal tyrosyl residue within tyrosine-containing flavinyl peptides. The fluorescence properties provide further confirmation of the identity of the synthetic and naturally obtained flavinyl peptides and of the interaction between the free-hydroxyl functions of the ribityl side chain and the thioether.
|
33de31e2-ac11-4665-8893-d1406f2ff0dc
| 0 |
High molecular weight deoxyribonucleic acid polymerase from crown gall tumor cells of periwinkle (Vinca rosea). A high molecular weight (6 S) plant DNA polymerase from axenic Vinca rosea tissue culture cells has been purified 2200-fold and characterized. The enzyme has a molecular weight of 105 000 (+/-5000).
|
33de31e2-ac11-4665-8893-d1406f2ff0dc
| 1 |
Sodium dodecyl sulfate-acrylamide gel electrophoresis of the purified enzyme yields polypeptide subunits having molecular weights of 70 000 and 34 000. The purified enzyme has a pH optimum of 7.5; a cation requirement optimum of 6 mM Mg2+ or 0.5 mM Mn2+; an apparent requirement for Zn2+;
|
33de31e2-ac11-4665-8893-d1406f2ff0dc
| 2 |
a Km of 1 muM for dTTP; and a 3.5-fold stimulation by 50 mM KCl. The enzyme is sensitive to N-ethylmaleimide (1 mM), heparin (0.1 muM), ethanol (5%), pyrophosphate (0.05 muM), and o-phenanthroline (0.1 mM) but is insensitive to rifamycin.
|
33de31e2-ac11-4665-8893-d1406f2ff0dc
| 3 |
Denatured DNA is found to be the best natural template, and only negligible activity can be demonstrated with the ribopolymer templates poly(dT)n-poly(rA)n and p(dT)10-poly(rA)n. In addition to the polymerization reaction, the enzyme catalyzes a pyrophosphate exchange reaction. Antibody to calf thymus 6-8S DNA polymerase does not inhibit DNA polymerase from Vinca rosea, suggesting no antigenic relationships between the mammalian and plant enzymes.
|
b644cea1-2ea4-4533-aa52-af5df506321e
| 0 |
Preparation, characterization, and chemical properties of the flavin coenzyme analogues 5-deazariboflavin, 5-deazariboflavin 5'-phosphate, and 5-deazariboflavin 5'-diphosphate, 5'leads to5'-adenosine ester. In order to facilitate interpretation of the deazaisoalloxazine system as a valid mechanistic probe of flavoenzyme catalysis, we have examined some of the fundamental chemical properties of this system.
|
b644cea1-2ea4-4533-aa52-af5df506321e
| 1 |
The enzymatic synthesis, on a micromole scale, of the flavin coenzyme analogues 5-deazariboflavin 5'-phosphate (deazaFMN) and 5-deazariboflavin 5'-diphosphate, 5' leads to 5'adenosine ester (deazaFAD) has been achieved. This latter synthesis is accomplished with a partially purified FAD synthetase complex (from Brevibacterium ammoniagenes), containing both phosphorylating and adenylylating activities, allowing direct conversion of the riboflavin analogue to the flavin adenine dinucleotide level.
|
b644cea1-2ea4-4533-aa52-af5df506321e
| 2 |
The structure of the reduced deazaflavin resulting from enzymatic and chemical reduction is established as the 1,5-dihydrodeazaflavin by proton magnetic resonance. Similarly, the C-5 position of the deazaflavins is demonstrated to be the locus for hydrogen transfer in deazaflavin redox reactions. Preparation of 1,5-dihydrodeazaflavins by sodium borohydride reduction stabilized them to autoxidation (t 1/2 approximately 40 h, 22 degrees C) although dihydrodeazaflavins are rapidly oxidized by other electron acceptors, including riboflavin, phenazine methosulfate, methylene blue, and dichlorophenolindophenol.
|
b644cea1-2ea4-4533-aa52-af5df506321e
| 3 |
Mixtures of oxidized and reduced deazaflavins undergo a rapid two-electron disproportionation (k = 22 M-1 S-1 0 degrees C), and oxidized deazaflavins form transient covalent adducts with nitroalkane anions at pH less than 5. Generalized methods for the synthesis of isotopically labeled flavin and deazaflavin coenzymes and their purification by adsorptive chromatography are given.
|
24eab260-4f6a-42ce-97be-009bd6aa8c1c
| 0 |
Enzyme-catalyzed redox reactions with the flavin analogues 5-deazariboflavin, 5-deazariboflavin 5'-phosphte, and 5-deazariboflavin 5'-diphosphate, 5' leads to 5'-adenosine ester. The ability of 5-deazaisoalloxazines to substitute for the isoalloxazine (flavin) coenzyme has been examined with several flavoenzymes. Without exception, the deazaflavin is recognized at the active site and undergoes a redox change in the presence of the specific enzyme substrate.
|
24eab260-4f6a-42ce-97be-009bd6aa8c1c
| 1 |
Thus, deazariboflavin is reduced catalytically by NADH in the presence of the Beneckea harveyi NAD(P)H:(flavin) oxidoreductase, the reaction proceeding to an equilibrium with an equilibrium constant near unity. This implies an E0 of -0.310 V for the deazariboflavindihydrodeazariboflavin couple, much lower than that for isoalloxazines.
|
24eab260-4f6a-42ce-97be-009bd6aa8c1c
| 2 |
With this enzyme, both riboflavin and deazariboflavin show the same stereospecificity with respect to the pyridine nucleotide, and despite a large difference in Vmax for the two, both have the same rate-determining step (hydrogen transfer). Direct transfer of the hydrogen is seen between the nicotinamide and deazariboflavin in both reaction directions.
|
24eab260-4f6a-42ce-97be-009bd6aa8c1c
| 3 |
DeazaFMN reconstituted yeast NADPH: (acceptor) oxidoreductase (Old Yellow Enzyme), and deazaFAD reconstituted D-amino acid:O2 oxidoreductase and Aspergillus niger D-glucose O2 oxidoreductase are all reduced by substrate at approximately 10(-5) the rate of holoenzyme; none are reoxidized by oxygen or any of the tested artificial electron acceptors, though deazaFADH-bound to D-amino acid:
|
24eab260-4f6a-42ce-97be-009bd6aa8c1c
| 4 |
O2 oxidoreductase is rapidly oxidized by the imino acid product. Direct hydrogen transfer from substrate to deazaflavin has been demonstrated for both deazaFAD-reconstituted oxidases. These data implicate deazaflavins as a unique probe of flavin catalysis, in that any mechanism for the flavin catalysis must account for the deazaflavin reactivity as well.
|
e66efd4e-4827-4632-8964-42355a55bd9b
| 0 |
Electrofocusing and kinetic studies of adult and embryonic chicken pyruvate kinases. Chicken embryos less than 15 days old contain only the K isozyme of pyruvate kinase, which appears to exist in vivo as an R,T conformational set with pI values of 7.2 and 6.6, respectively. Sets of lower pI and higher pI K-isozyme variants also are obtained.
|
e66efd4e-4827-4632-8964-42355a55bd9b
| 1 |
Whole embryos of 15 days or more of development show progressively increasing amounts of higher pI, lower K0.5S enzymatic variants. Tissue distribution and kinetic properties suggest that the highest pI form (pH 8.8-9.0) is an M-isozyme analogue. The intermediate forms are postulated to be hybrids.
|
e66efd4e-4827-4632-8964-42355a55bd9b
| 2 |
Adult liver extracts contain only the embryonic K isozyme; no evidence for an L-isozyme analogue was obtained. All major forms of the enzymes are compared with respect to saturation by phosphoenolpyruvate in the absence of effector and in the presence of fructose 1,6-diphosphate, alanine, serine, phenylalanine, tryptophan, and/or Mg-ATP.
|
d1ebfd35-7d47-4f95-8b61-128064e4dab9
| 0 |
Characterization of a cytochrome P-450 dependent monoterpene hydroxylase from the higher plant Vinca rosea. A monooxygenase isolated from 5-day old etiolated Vinca rosea seedlings was shown to catalyze the hydroxylation of the monoterpene alcohols, geraniol and nerol, to their corresponding 10-hydroxy derivatives. Hydroxylase activity was inpendent upon NADPH (neither NADH nor combination of NADH, NADP+ and ATP served as substitutes) and O2.
|
d1ebfd35-7d47-4f95-8b61-128064e4dab9
| 1 |
Geraniol hydroxylation was enhanced by dithiothreitol (monothiols were less effective) and inhibited by phospholipases, thiol reagents, metyrapone, and cytochrome c, as well as other inhibitors of cytochrome P-450 systems. Geraniol was hydroxylated at a faster rate than nerol, but the alcohols possessed similar apparent Km values.
|
d1ebfd35-7d47-4f95-8b61-128064e4dab9
| 2 |
The membrane-bound hydroxylase was solubilized by treatment with sodium cholate, Renex-30, or Lubrol-WX. Cholate-treated enzyme was resolved by DEAE-cellulose chromatography and reconstitution of the hydroxylase was effected utilizing different fractions containing cytochrome P-450, a NADPH-cytochrome c reductase, and lipid.
|
90386f9e-70b5-450a-9309-0724390de5ff
| 0 |
Methionine sulfoxide cytochrome c. Cytochrome c has been chemically modified by methylene blue mediated photooxidation. It is established that the methionine residues of the protein have been specifically converted to methionine sulfoxide residues. No oxidation of any other amino acid residues or the cysteine thioether bridges of the molecule occurs during the photooxidation reaction.
|
90386f9e-70b5-450a-9309-0724390de5ff
| 1 |
The absorbance spectrum of methionine sulfoxide ferricytochrome c at neutrality is similar to that of the unmodified protein except for an increase in the extinction coefficient of the Soret absorbance band and for the complete loss of the ligand sensitive 695 nm absorbance band in the spectrum of the derivative.
|
90386f9e-70b5-450a-9309-0724390de5ff
| 2 |
The protein remains in the low spin configuration which implies the retention of two strong field ligands. Spin state sensitive spectral titrations and model studies of heme peptides indicate that the sixth ligand is definitely not provided by a lysine residue but may be methionine-80 sulfoxide coordinated via its sulfur atom.
|
90386f9e-70b5-450a-9309-0724390de5ff
| 3 |
Circular dichroism spectra indicate that the heme crevice of methionine sulfoxide ferri- and ferrocytochrome c is weakened relative to native cytochrome c. The redox potential of methionine sulfoxide cytochrome c is 184 mV which is markedly diminished from the 260 mV redox potential of native cytochrome c. The modified protein is equivalent to native cytochrome c as a substrate for cytochrome oxidase and is not autoxidizable at neutral pH but is virtually inactive with succinate-cytochrome c reductase.
|
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