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cda396a5-cde9-44b8-85d6-df03e65ac306
| 1 |
It appears that the protein is monomeric in organic solution. In water, only one component is present but the molecules behave as a polydisperse system of associating molecules. Hydrophobic interacitons seem to be important for this polymerisation which does not appear to be accompanied by the formation of beta-structure.
|
cda396a5-cde9-44b8-85d6-df03e65ac306
| 2 |
After the transfer of the protein from organic solution to water, the ESR spectra of the protein labelled on the free SH groups show an heterogeneity in the motional environment of the label which permits to assume that different areas of association exist in the polymeric molecule.
|
4c6dfeeb-de91-4ab3-8f21-9bcd6c1a2b66
| 0 |
Response of the glycolysis of human erythrocytes to the transition from the oxygenated to the deoxygenated state at constant intracellular pH. The time course of the rate of the glycolysis of human erythrocytes and of some metabolites were determined before and after rapid deoxygenation at constant intracellular pH. For this purpose stripped deoxygenated haemoglobin was used as a rapid oxygen acceptor.
|
4c6dfeeb-de91-4ab3-8f21-9bcd6c1a2b66
| 1 |
Deoxygenation causes an increase of the glycolytic rate by 26%. Glucose 6-phosphate is decreased while the adenine nucleotides and 2,3-bisphosphoglycerate remain constant. Fructose 1,6-bisphosphate and the triose phosphates decrease transiently before rising. The data can be explained by increased binding of phosphocompounds to deoxygenated as compared with oxygenated haemoglobin.
|
4c6dfeeb-de91-4ab3-8f21-9bcd6c1a2b66
| 2 |
Thereby the control enzymes hexokinase and phosphofructokinase are influenced. It is concluded that under physiological conditions changes in the oxygenation state of haemoglobin per se alter the glycolytic rate.
|
e3c77820-70e4-44aa-ad83-bd8d75ec0098
| 0 |
Intracellular pH of frog sartorius muscle. A weak base, morpholine, has been labelled with 3H and tested for its suitability as an indicator for intracellular pH, by distribution in the tissue water of frog sartorius muscle in the species Hyla litoria. Its pK'a at 20 degrees C in a solution of the same ionic strength as frog Ringer was found to be 8.45
|
e3c77820-70e4-44aa-ad83-bd8d75ec0098
| 1 |
+/- 0.02, which is in the range of maximal sensitivity. Morpholine equilibrated with the tissue in 17 h; it was shown that it was not bound to intracellular constituents, that it was not metabolised nor toxic in the concentrations used; it was therefore judged suitable as a pH indcator.
|
e3c77820-70e4-44aa-ad83-bd8d75ec0098
| 2 |
Intracellular pH was then measured by distribution of morpholine (6.985 +/- 0.08), nicotine (6.915 +/- 0.03) and the weak acid 5,5'-dimethyl-2,4-oxazolidinedione (7.10 +/- 0.05) and the pH-sensitive microelectrodes (5.9, the equilibrium value). It was shown that the four significantly different values could not be reconciled in terms of experimental error, heterogeneity of intracellular pH, liquid junction potential differences, or binding of indicator molecules inside the fibre.
|
e3c77820-70e4-44aa-ad83-bd8d75ec0098
| 3 |
They could, however, be reconciled if the fibre water had different structure and solvent properties from the extracellular water and all ions were distributed across the membrane as between two liquid phases containing different solvents. Then the H+ would be in equilibrium, as shown by the microelectrode measurement, but intracellular pH would be indeterminable and probably greater than 6.
|
3d403564-cd52-49d9-9952-503af9621a41
| 0 |
Activation of murine lymphocytes by cyclic guanosine 3',5'-monophosphate: specificity and role in mitogen activity. Cyclic guanosine 3',5'-monophosphate (cyclic GMP) stimulates nucleic acid synthesis in lymphocytes, and has been implicated as the intracellular effector of the actions of mitogenic agents on these cells.
|
3d403564-cd52-49d9-9952-503af9621a41
| 1 |
In the present study, we examined the specificity of the mitogenic activity of cyclic GMP and of its 8-bromo (Br) derivatives, and the effects of the T cell mitogens, concanavalin A, phytohemagglutinin, and staphylococcal entertoxin B (SEB) on the cyclic GMP content and guanylate cyclase activity of mouse splenic lymphocytes.
|
3d403564-cd52-49d9-9952-503af9621a41
| 2 |
Cyclic GMP and guanosine modestly increased the incorporation of [3H] thymidine into DNA by cultured lymphocytes, but were far less effective than their 8-Br-guanosine and 8-Br-5'-GMP exceeded that of 8-Br-cyclic GMP, when tested in the presence and absence of serum in the culture media.
|
3d403564-cd52-49d9-9952-503af9621a41
| 3 |
Combined addition of maximal doses of these nucleotides did not give additive stimulatory effects, suggesting an action on a common subpopulation of cells, and possibly a common mechanism. By contrast, cyclic AMP, 8-Br-cyclic AMP, 8-Br-adenosine, cholera toxin and prostaglandin E1 suppressed both basal [3H]thymidine incorporation and stimulation of this parameter by T-cell mitogens and the guanine nucleotides.
|
3d403564-cd52-49d9-9952-503af9621a41
| 4 |
Rapid effects of concanavalin A, phytohemagglutinin, SEB, guanosine, 5'-GMP, 8-Br-guanosine, and 8-Br-5'-GMP on the cyclic GMP content of murine lymphocytes could not be demonstrated. Similarly, concanavalin A, phytohemagglutinin and SEB failed to alter guanylate cyclase activity when added directly to cellular homogenates or pre-incubated with intact cells.
|
3d403564-cd52-49d9-9952-503af9621a41
| 5 |
Conversely, carbamylcholine rapidly increased lymphocyte cyclic GMP but was not mitogenic. These results are consistent with the hypothesis that cyclic GMP and cyclic AMP are antagonistic in their influence on lymphocyte mitogenesis. However, they also demonstrate that related nucleotides are more potent mitogens than cyclic GMP itself and suggest that activation of murine lymphocytes by concanavalin A, phytohemagglutinin and SEB may not be mediated by rapid increases in cellular cyclic GMP content.
|
3d403564-cd52-49d9-9952-503af9621a41
| 6 |
Since high concentrations of exogenous cyclic GMP and related nucleotides must be used to influence DNA synthesis, the biologic significance of this effect remains uncertain.
|
deb9b244-6126-4921-be6c-b713e430b986
| 0 |
Characterization of protein kinases from bovine parotid glands. The effect of tolbutamide and its derivative on these partially purified enzymes. 1. Four fractions of protein kinase (EC 2.7.1.37) activity (Peak IH, IIH, IIIC and IVC) have been resolved and partially purified from the 100 000 X g supernatant fraction of bovine parotid glands by DEAE-cellulose and phosphocellulose chromatographies.
|
deb9b244-6126-4921-be6c-b713e430b986
| 1 |
2. The protein kinases of Peak IH and IIH were adenosine 3',5'-monophosphate (cyclic AMP) -dependent and had similar enzymic properties. The enzyme activities of Peak IIIC and IVC were cyclic-AMP independent, but there were some distinct differences between their properties. The protein kinase in Peak IIIC was activated by 0.2
|
deb9b244-6126-4921-be6c-b713e430b986
| 2 |
M NaCl or KCl and phosphorylated casein preferentially as the substrate, utilizing only ATP as a phosphate donor. On the other hand, the protein kinase in Peak IVC was inhibited by univalent salts and preferred phosvitin to casein, utilizing either ATP or GTP as a phosphate donor. 3.
|
deb9b244-6126-4921-be6c-b713e430b986
| 3 |
Tolbutamide increased the Km value for ATP and the dissociation constant for cyclic AMP, resulting in the inhibition of cyclic-AMP dependent protein kinase activity in the presence of cyclic AMP. Tolbtamide and its carboxy derivative, 1-butyl-3-p-carboxyphenylsulfonylurea, exerted almost no inhibitory effect on either the cyclic-AMP dependent protein kinase activities in the absence of cyclic AMP or on the cyclic-AMP independent protein kinase activities.
|
a6d55482-bd9e-48f9-a74e-52de188f45a5
| 0 |
A study of the single polypeptide nature of rhodanese. A comparison of different preparations. The enzyme rhodanese (EC 2.8.1.1) appears as a single polypeptide chain protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight of this species is approx. 33 000. This contrasts with previous reports that rhodanese behaves on gel filtration chromatography as a rapidly equilibrating monomer-dimer system composed of identical subunits with a molecular weight of 18 500.
|
a6d55482-bd9e-48f9-a74e-52de188f45a5
| 1 |
We have investigated this apparent discrepancy by isolating the enzyme by the two different preparative procedures used in the above investigations. The two crystalline samples were subjected to gel filtration chromatography under a wide variety of conditions and to sodium dodecyl sulfate disc gel electrophoresis. The two preparations yielded rhodanese which behaved identically and no evidence for the monomeric species was obtained under any experimental condition tested.
|
a6d55482-bd9e-48f9-a74e-52de188f45a5
| 2 |
Thin-layer gel chromatography of clarified liver homogenates gave no evidence of rhodanese species other than that present in the purified samples. The variation in molecular weights observed in gel filtration chromatography may be a reflection of the conformational mobility of the enzyme leading to solvent-dependent changes in Stokes radius.
|
a6d55482-bd9e-48f9-a74e-52de188f45a5
| 3 |
If rhodanese is dimeric, special interactions must stabilize it under the conditions tested here.
|
4cf59ef6-087c-49ad-a6eb-041bd983310b
| 0 |
Characterization of intracellular esterase A from Bacillus subtilis. Esterase A (EC 3.1.1.1) obtained by sonic disruption of Bacillus subtilis SR22 (spoA12, trpC2) was purified approximately 400-fold by differential chemical and heating precipitation, DEAE-cellulose chromatography, and Bio-Rad P-150 gel filtration chromatography, with an overall yield of 59%.
|
4cf59ef6-087c-49ad-a6eb-041bd983310b
| 1 |
The purified enzyme hydrolyzed both aliphatic and aromatic acetate esters at substrate concentrations of 0.25 M but did not hydrolyze amino acid esters. Aliphatic alcohols did not inhibit the hydrolysis of p-nitrophenyl acetate; the most potent inhibitors of esterase activity were mercuric chloride, diisopropylfluorophosphate, eserine, and sodium fluoride.
|
4ab71573-5c0a-47f4-ac1c-fd4717f99c61
| 0 |
[Cow's milk alkaline phospharase. II. Subunit structure, metalloproteic nature and kinetic parameters (author's transl)]. Alkaline phosphatase (EC 3.1.3.1) from cow's milk as a dimer comprising two identical or very similar subunits of about 85 000 molecular weight. The enzyme contains 4.9 +/- 0.6
|
4ab71573-5c0a-47f4-ac1c-fd4717f99c61
| 1 |
gatoms of zinc per mol of protein. The essential kinetic properties are the same as those of other alkaline phosphatases: variation of pH optimum value, the lack of specificity, increase of Km and V with pH value. The phosphotransferase activity is enlarged, at constant concentration of acceptor, with an increasing concentration of donor.
|
4ab71573-5c0a-47f4-ac1c-fd4717f99c61
| 2 |
The small size of molecules and the presence of hydroxyls and amino groups increase the percentage of transfer phosphate. The phosphotransferase reaction is better with the D-isomer of serine and the enzyme possesses a more important affinity for the D-phosphoserine.
|
1e3ec5eb-e9ec-4cc9-b3c1-3fc76d5dac63
| 0 |
Kinetic properties of pulmonary angiotensin-converting enzyme. Hydrolysis of hippurylglycylglycine. Some of the kinetic properties of angiotensin-converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) purified from hog lung have been determined using hippurylglycylglycine as substrate. The effects of pH and ionic environment on enzyme activity are complex and interdependent.
|
1e3ec5eb-e9ec-4cc9-b3c1-3fc76d5dac63
| 1 |
At 0.1 M NaCl, the pH-activity curve shows an abrupt decrease in V/Km as the pH rises from 6 to 6.5, implying that ionization of a group in the enzyme with a pK in this range aids in binding of the substrate. Chloride is required for enzyme activity;
|
1e3ec5eb-e9ec-4cc9-b3c1-3fc76d5dac63
| 2 |
there are two phases in the effect of NaCl. At both pH 6 AND 8, THE FIRST PHASE (UP TO 0.1 M NaCl) is activation. The second phase (above 0.1 M) at pH 6 is inhibition, while at pH 8 there is further activation which appears to be dependent upon ionic strength rather than a specific Cl-effect.
|
1e3ec5eb-e9ec-4cc9-b3c1-3fc76d5dac63
| 3 |
Activation by cobalt and inhibition by EDTA are somewhat more effective at pH 6 than at pH 8. The nonapeptide inhibitor less than Glu-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro is nearly equipotent at both pH 6 and 8, but Arg-Pro-Pro is more inhibitory at pH 8 than at pH 6.
|
95fcaa24-d352-4db2-9999-632a379393a6
| 0 |
Separation and properties of the NAD-linked and NADP-linked isozymes of succinic semialdehyde dehydrogenase in Euglena gracilis z. Euglena gracilis z contained two succinic semialdehyde dehydrogenases (EC 1.2.1.16), one requiring NAD and the other NADP, and these isozymes were separated from each other and partially purified. The NAD-linked isozyme was relatively stable on storage at 5 degrees C whereas the NADP-linked one was extremely unstable unless 30% glycerol or ethyleneglycol was added.
|
95fcaa24-d352-4db2-9999-632a379393a6
| 1 |
The optimum pH was 8.7 and optimum temperature 35-45 degrees C for both isozymes. They were inhibited by Zn2+ and activated, particularly the NAD-linked enzyme, by K+. Sulfhydryl reagents activated both isozymes. The Km values for succinic semialdehyde were 1.66 - 10(-4) M with the NAD-linked isozyme and 1.06
|
95fcaa24-d352-4db2-9999-632a379393a6
| 2 |
- 10(-3) M with the NADP-linked one. The NADP-linked isozyme was induced by glutamate while the NAD-linked one was not. Probable roles of these isozymes in the physiology of Euglena gracilis are discussed.
|
706932ef-7383-47d9-9c5e-b84563cbb63e
| 0 |
Activation of tyrosine hydroxylase by polyanions and salts. An electrostatic effect. The activity of a partially purified preparation of tyrosine hydroxylase (EC 1.14.16.2) from the bovine caudate nucleus was increased by heparin, chondroitin sulfate, phosphatidylserine, polyacrylic acid, polyvinyl sulfuric acid and both poly-D-, and poly-L-glutamic acids, all polyanions.
|
706932ef-7383-47d9-9c5e-b84563cbb63e
| 1 |
A variety of salts both activated the enzyme and prevented the activation by the polyanions. The observations that activity is increased when the enzyme interacts with salts and with macromolecules of high negative charge density are used to infer a model for these interactions and for the structural change in the enzyme that accompanies activation.
|
2e13a5aa-05a3-4595-b369-6d03295b1b40
| 0 |
Glycolipid glycosyl transferases of a hamster cell line in culture. I. Kinetic constants, substrate and donor nucleotide sugar specificities. The properties of enzymes catalysing the transfer of a galactose from UDP-galactose to exogenous ceramide monohexoside and ceramide di-hexoside derived from the Syrian hamster cell line NIL 2 were studied.
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2e13a5aa-05a3-4595-b369-6d03295b1b40
| 1 |
The products of these enzymes were characterized by chemical and enzymatic methods. Kinetic analyses showed that the enzymes are susceptible to inhibition and activation by a number of substrate analogues. The kinetic and inhibition constants, glycolipid substrate specificity and nucleotide sugar donor specificity have been studied.
|
df9edea5-a7e6-47ec-9074-d9802d67378e
| 0 |
Pigeon liver diacetyl reductase. Effects of pH on the kinetic parameters of the reaction. (1) The pH dependence of the kinetic parameters of the reaction catalyzed by pigeon liver diacetyl reductase (EC 1.1.1.5) was investigated in the pH range 5.1-8.6. (2) From the results obtained it is postulated that:
|
df9edea5-a7e6-47ec-9074-d9802d67378e
| 1 |
(a), a group of pK around 7, active in the protonated form, participates in the interaction of the enzyme with NADH and NAD. (b), a second group with a pK of 8.4, active in the protonated form too, takes part in the binding of diacetyl to E-NADH.
|
df9edea5-a7e6-47ec-9074-d9802d67378e
| 2 |
(c) A third group of pK about 4.7-5, active in the unprotonated form, is involved at least in the dissociation of the complex E-NAD and in the attachment of diacetyl to E-NADH.
|
9c768574-0d25-4792-a508-59301f1ffd5a
| 0 |
Alkylation of cysteinyl residues of pig heart NAD-specific isocitrate dehydrogenase by iodoacetate. Pig heart NAD-specific isocitrate dehydrogenase is inactivated by reaction with iodoacetate at pH 6.0. Loss of activity can be attributed to the formation of 1-2 mol of carboxymethyl-cysteine per peptide chain. The rate of inactivation is markedly decreased by the combined addition of Mn2+ and isocitrate, but not by alpha-ketoglutarate, the coenzyme NAD or the allosteric activator ADP.
|
9c768574-0d25-4792-a508-59301f1ffd5a
| 1 |
The substrate concentration dependence of the decreased rate of inactivation yields a dissociation constant of 1.6 mM for the enzyme-manganous-dibasic isocitrate complex, a value that is 50 times higher than the Km for this substrate. This result suggests that in protecting the enzyme against iodoacetate, isocitrate may bind to a region distinct from the catalytic site.
|
9c768574-0d25-4792-a508-59301f1ffd5a
| 2 |
Isocitrate and Mn2+ also prevent thermal denaturation, with an affinity for the enzyme close to that observed for the iodoacetate-sensitive site. The alkylatable cysteine residues may contribute to a manganous-isocitrate binding site which is responsible for stabilizing an active conformation of the enzyme.
|
d5c16007-09ea-4ae5-828b-d50a46511ee0
| 0 |
Purification and properties of NADP-dependent glutamate dehydrogenase from yeast nuclear fractions. 1. NADP-dependent glutamate dehydrogenase (EC 1.4.1.4) extracted from nuclear fractions of Saccharomyces cerevisiae was partially purified. The final purification achieved was over 100-fold over the initial extract. 2. Cellulose acetate electrophoresis shows that the preparation is close to homogeneity and that the enzyme is slightly more anionic than cytoplasmic glutamate dehydrogenase.
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d5c16007-09ea-4ae5-828b-d50a46511ee0
| 1 |
3. The response of the nuclear activity to variation of pH, of inorganic phosphate and other electrolyte concentration and of the concentration of the reaction substrates has been investigated. Several differences were detected in comparison with cytoplasmic glutamate dehydrogenase.
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b3b4d4d2-0beb-418b-a542-39c51142fd09
| 0 |
Comparative kinetic studies on the L-type pyruvate kinase from rat liver and the enzyme phosphorylated by cyclic 3', 5'-AMP-stimulated protein kinase. The kinetics of rat liver L-type pyruvate kinase (EC 2.7.1.40), phosphorylated with cyclic AMP-stimulated protein kinase from the same source, and the unphosphorylated enzyme have been compared.
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b3b4d4d2-0beb-418b-a542-39c51142fd09
| 1 |
The effects of pH and various concentrations of substrates, Mg2+, K+ and modifiers were studied. In the absence of fructose 1, 6-diphosphate at pH 7.3, the phosphorylated pyruvate kinase appeared to have a lower affinity for phosphoenolpyruvate (K0.5=0.8 mM) than the unphosphorylated enzyme (K0.5
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b3b4d4d2-0beb-418b-a542-39c51142fd09
| 2 |
=0.3 mM). The enzyme activity vs. phosphoenolpyruvate concentration curve was more sigmoidal for the phosphorylated enzyme with a Hill coefficient of 2.6 compared to 1.6 for the unphosphorylated enzyme. Fructose 1, 6-diphosphate increased the apparent affinity of both enzyme forms for phosphoenolpyruvate. At saturating concentrations of this activator, the kinetics of both enzyme forms were transformed to approximately the same hyperbolic curve, with a Hill coefficient of 1.0
|
b3b4d4d2-0beb-418b-a542-39c51142fd09
| 3 |
and K0.5 of about 0.04 mM for phosphoenolpyruvate. The apparent affinity of the enzyme for fructose 1, 6-diphosphate was high at 0.2 mM phosphoenolpyruvate with a K0.5=0.06 muM for the unphosphorylated pyruvate kinase and 0.13 muM for the phosphorylated enzyme. However, in the presence of 0.5
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b3b4d4d2-0beb-418b-a542-39c51142fd09
| 4 |
mM alanine plus 1.5 mM ATP, a higher fructose 1, 6-diphosphate concentration was needed for activation, with K0.5 of 0.4 muM for the unphosphorylated enzyme and of 1.4 muM for the phosphorylated enzyme. The results obtained strongly indicate that phosphorylation of pyruvate kinase may also inhibit the enzyme in vivo.
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b3b4d4d2-0beb-418b-a542-39c51142fd09
| 5 |
Such an inhibition should be important during gluconeogenesis.
|
c9e67f67-23d8-4d6b-8977-370f2e5653f8
| 0 |
Denaturation-induced disulfide formation in the enzyme rhodanese. The effect of denaturants on the quantitation of free sulfhydryl groups in the enzyme rhodanese (thiosulfate sulfurtransferase, EC 2.8.1.1) has been reinvestigated in some detail. The sulfhydryl assay with the colorimetric reagent 5, 5'-dithio-bis (2-nitrobenzoic acid) Nbs2 shows four sulfhydryl groups per enzyme molecule (mol.
|
c9e67f67-23d8-4d6b-8977-370f2e5653f8
| 1 |
wt. 32 300) when the colorimetric reagent is added to the assay mixture before the denaturant, sodium dodecyl sulfate. On the other hand, only two sulfhydryl groups per molecule are observed when Nbs2 is added after denaturation has been initiated. The time dependence observed in this latter procedure indicates that the loss of the two groups is rapid and permanent.
|
c9e67f67-23d8-4d6b-8977-370f2e5653f8
| 2 |
The results depend on the denaturant used: urea acts like sodium dodecyl sulfate while guanidine reveals four sulfhydryl groups independent of reagent order. The assay also gives four sulfhydryl groups independent of reagent order. The assay also gives four sulfhydryl groups independent of reagent order with urea or sodium dodecyl sulfate under conditions which are expected to limit metal ion-catalyzed oxidation of sulfhydryl groups (e.
|
c9e67f67-23d8-4d6b-8977-370f2e5653f8
| 3 |
g. oxygen exclusion or metal ion chelation). Recent studies have shown that rhodanese has a molecular weight of 32 600, no disulfides and four sulfhydryl groups per molecule. These results together with the observations reported here are taken to indicate that a disulfide can be formed during denaturation of rhodanese and that the pathway of denaturation determines the result obtained.
|
7acceb3a-afb2-47f5-b79e-75c09f9db7ee
| 0 |
Studies on a 3beta-hydroxysteroid sulphotransferase from rat liver. A steroid sulphotransferase (EC 2.8.2.2) was partially purified from female rat liver. The enzyme was active towards the substrates, dehydroepiandrosterone, epiandrosterone and pregnenolone but was inactive towards oestrogens, cholesterol and ergocalciferol. A pH optimum of 5.0 was recorded but the enzyme was unstable at low pH.
|
7acceb3a-afb2-47f5-b79e-75c09f9db7ee
| 1 |
The enzyme was stimulated slightly by the addition of reducing agents and inhibited by p-chloromercuribenzoate and HgCl2. Crude enzyme activity was markedly stimulated by divalent cations but this effect was not observed with purified enzyme. A Km of 13 muM was calculated for the donor substrate 3'-phosphoadenylyl sulphate and the acceptor substrate, dehydroepiandrosterone had a Km value of 6 muM.
|
7acceb3a-afb2-47f5-b79e-75c09f9db7ee
| 2 |
The enzyme appeared to be highly susceptible to product inhibition by adenosine 3', 5'-diphosphate.
|
4fce7f5a-f6af-41ed-aef6-103c651ab9cb
| 0 |
An ESR study of the influence of some physico-chemical factors on the conformation of a postsynaptic acetylcholinesterase. 1. In a previous ESR study of a membrane acetylcholinesterase (EC 3.1.1.7) we found, contrary to observations by other authors, spectra indicating that the active serine might be located in a pocket of the enzyme surface.
|
4fce7f5a-f6af-41ed-aef6-103c651ab9cb
| 1 |
In order to inquire into this possibility, ESR spectra were studied under the influence of different physico-chemical factors known to cause an unfolding of proteins. 2. The active serine of the postsynaptic membrane acetylcholinesterase of Torpedo marmorata electric organ was spin labeled using 1-oxyl-2, 2, 6, 6-tetramethyl-4-piperidinyletoxyphosphonofluoridate.
|
4fce7f5a-f6af-41ed-aef6-103c651ab9cb
| 2 |
3. The effect of the chosen physico-chemical factors was an increase in the rotational freedom of spin labels; this result corroborates the suggestion that the active center of our acetylcholinesterase preparation is located in a pocket.
|
fcf1eaa8-5ec2-4f26-a03f-66ede9e6638d
| 0 |
Presence and androgen control of an alkaline phosphatase in the nucleus of rat ventral prostate. The presence of alkaline phosphatase (EC 3.1.3.1) activity has been demonstrated in nuclei of rat ventral prostate. This enzyme activity remained after washing of isolated nuclei with 0.5% Triton X-100; an acid phosphatase initially present with the nuclear fraction was removed by this treatment.
|
fcf1eaa8-5ec2-4f26-a03f-66ede9e6638d
| 1 |
The nuclear alkaline phosphatase, examined by utilizing p-nitrophenyl phosphate as substrate, had a pH optimum of 9.5-10.3, and a broad substrate specificity: p-nitrophenyl phosphate greater than phosphothreonine greater than beta-glycerophosphate greater than phosphoserine. The nuclear phosphatase was sensitive to denaturation by heat or urea treatments and was also inhibited by Pi, L-phenylalanine, homoarginine, dithiothreitol, and EDTA.
|
fcf1eaa8-5ec2-4f26-a03f-66ede9e6638d
| 2 |
The EDTA-inhibited enzyme was maximally reactivated by Zn2+, although Mg2+, or Ca2+ were also effective at somewhat higher concentrations. Orchiectomy of adult rats resulted in an increase in the nuclear alkaline phosphatase activity (2-3-fold at 24 or 48 h postorchiectomy). A decline in the protein:
|
fcf1eaa8-5ec2-4f26-a03f-66ede9e6638d
| 3 |
DNA ratio also occurred following orchiectomy, but the increase in phosphatase specific activity was evident whether expressed per unit of protein or per unit of DNA. Testosterone replacement following orchiectomy abolished the increase in nuclear phosphatase activity. The results suggest that the prostatic nuclear alkaline phosphatase may be involved in events related to inactivation of the prostate nucleus following androgen deprivation.
|
be35f384-8431-4c88-b91c-3a10d07f8bd4
| 0 |
Removal of phosphate groups from casein with potato acid phosphatase. Potato acid phosphatase (EC 3.1.3.2) was used to remove the eight phosphate groups from alphas1-casein. Unlike most acid phosphatases, which are active at pH 6.0 or below, potato acid phosphatase can catalyze the dephosphorylation of alphas1-casein at pH 7.0
|
be35f384-8431-4c88-b91c-3a10d07f8bd4
| 1 |
. Although phosphate inhibition is considerable (K1=0.42 mM phosphate), the phosphate ions produced by the dephosphorylation of casein can be removed by dialysis, allowing the reaction to go to completion. The dephosphorylated alphas1-casein is homogeneous on gel electrophoresis with a slower mobility than native alphas1-casein and has an amino acid composition which is identical to native alphas1-casein.
|
be35f384-8431-4c88-b91c-3a10d07f8bd4
| 2 |
Thus the removal of phosphate groups from casein does not alter its primary structure. Potato acid phosphatase also removed the phosphate groups from other phosphoproteins, such as beta-casein, riboflavin binding protein, pepsinogen, ovalbumin, and phosvitin.
|
6a80b157-4c8f-490e-bdfc-02f580cab37b
| 0 |
Multiple forms of cyclic nucleotide phosphodiesterase in pig epidermis. Pig epidermal cyclic nucleotide phosphodiesterases (EC 3.1.4.16) have been partially purified by DEAE-cellulose column chromatography. At least three different forms of the epidermal phosphodiesterases were identified. They were cyclic GMP-specific, cyclic GMP- and cyclic AMP-hydrolyzing and apparently a cyclic AMP-specific enzyme:
|
6a80b157-4c8f-490e-bdfc-02f580cab37b
| 1 |
the first two forms were soluble and the last was the particulate enzyme. The cyclic GMP-specific soluble fraction had a relatively low Km, the cyclic GMP- and cyclic AMP-hydrolyzing fraction had a high Km for the respective substrates and the third particulate enzyme had both high and low Km values for cyclic AMP.
|
6a80b157-4c8f-490e-bdfc-02f580cab37b
| 2 |
The cyclic GMP-hydrolyzing enzyme was localized almost entirely in the soluble fraction, whereas cyclic AMP-hydrolyzing enzyme was distributed to both soluble and particulate fractions. Thus, our studies show that the multiple forms of pig epidermal enzyme differ distinctly in their substrate affinity, specificity and subcellular distribution.
|
111b062c-cf17-4a64-aac0-abdbbb84af78
| 0 |
Ascorbic acid-2-sulfate sulfhohydrolase activity of human arylsulfatase A. Pure human arylsulfatase A (EC 3.1.6.1) was found to hydrolyze ascorbic acid 2-sulfate to ascorbic acid and inorganic sulfate at rates from 200 to 2000 mumol/mg per h depending on the method of assay. This rate was lower than that observed with the synthetic substrate 4-nitrocatechol sulfate, but higher than that seen with the physiological substrate cerebroside sulfate.
|
111b062c-cf17-4a64-aac0-abdbbb84af78
| 1 |
Extracts of cultured fibroblasts from normal subjects were also shown to hydrolyze ascorbic acid 2-sulfate; extracts of fibroblasts from patients with metachromatic leukodystrophy, known to be deficient in arylsulfatase A, did not. Similarly, hydrolysis of ascorbic acid 2-sulfate was not observed when a partially purified preparation of human arylsulfatase B was tested under a variety of conditions.
|
111b062c-cf17-4a64-aac0-abdbbb84af78
| 2 |
Thus, in the human, arylsulfatase A appears to be the major, if not the only, ascorbic acid-2-sulfate sulfohydrolase.
|
3091ac2e-dadc-4733-b469-72825bc485f0
| 0 |
Human alpha-fucosidase. Single residual enzymatic form in fucosidosis. Four major forms of alpha-fucosidase (EC 3.2.1.51) activity were separated by isoelectrofocusing from sera of normal control individuals. All forms shifted towards less acidic pI values after neuraminidase treatment. In two patients affected with fucosidosis, only a single major acidic peak was observed and this was affected to a lesser degree by neuraminidase treatment.
|
3091ac2e-dadc-4733-b469-72825bc485f0
| 1 |
The kinetics of heat inactivation of the residual activity found in these two patients showed two decay rates while the controls showed only one rate. These data are considered in relation to the hypothesis of the existence of interconvertible thermolabile and thermostable forms of the enzyme which has been discussed in the preceeding paper.
|
3091ac2e-dadc-4733-b469-72825bc485f0
| 2 |
The residual alpha-fucosidase found in patients could be structurally altered so that its ability to form the thermostable higher molecular weight aggregates is impaired.
|
31fbf2a3-61c0-4971-8a26-342a1fcd4027
| 0 |
Separation of two PZ-peptidases from bovine dental follicle. Two PZ-peptidases (EC 3.4.-) (A and B) cleaving a synthetic substrate for collagenase, 4-phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg (PZ-peptide) have been separated from the particulate fraction of bovine dental follicle.
|
31fbf2a3-61c0-4971-8a26-342a1fcd4027
| 1 |
PZ-peptidase A had a molecular weight of 220 000, an optimum pH at 8.0-8.5, and a Km value of 67 muM toward PZ-peptide at pH 7.1, whereas PZ-peptidase B had a molecular weight of 20 000, an optimum pH at 6.5-6.7, and a Km value of 400 muM toward PZ-peptide at pH 7.1
|
31fbf2a3-61c0-4971-8a26-342a1fcd4027
| 2 |
. Two similar enzymes were also isolated from the soluble fraction. Since the pH-activity curve of the crude tissue preparations such as homogenate, microsomes and soluble supernatant had two peaks at 6.5-6.7 and 8.0-8.5, both PZ-peptidase A and B may exist in situ as two independent active enzymes.
|
d9dbe33d-948e-4a42-aa55-3260bb2f8dbe
| 0 |
Properties of the major carboxypeptidase in the larvae of the webbing clothes moth, Tineola bisselliella. The larvae of the webbing clothes moth, Tineola bisselliella contain two carboxypeptidases (EC 3.4.12-) and one of these has been purified by preparative polyacrylamide gel electrophoresis. Its pH optimum for the hydrolysis of N-benzyloxycarbonyl-glycyl-leucine was pH 7.5
|
d9dbe33d-948e-4a42-aa55-3260bb2f8dbe
| 1 |
-7.7 and its molecular weight as judged by gel filtration was 72 000. It is strongly inhibited by disopropylfluorophosphate, thiol reagents and some metal cations and also by 1:10 phenanthroline but not EDTA. Km and V values for the hydrolysis of 13 N-acyl dipeptides were determined.
|
d9dbe33d-948e-4a42-aa55-3260bb2f8dbe
| 2 |
The enzyme has a strong preference for neutral aliphatic amino acid residues and does not hydrolyse C-terminal proline, arginine or lysine. It is a true carboxypeptidase, requiring an L-amino acid in the C-terminal position, with a free carboxyl group and hydrolysing peptide substrates consecutively from the C-terminal end.
|
d9dbe33d-948e-4a42-aa55-3260bb2f8dbe
| 3 |
Dipeptides are cleaved much more slosly than tripeptides or N-acyl dipeptides.
|
695738ad-a8bc-420c-ab52-5efaf3f60154
| 0 |
Cathepsins B1 from human fetal membranes. Cathepsins B1 (EC 3.4.22.1) were isolated from fetal membranes of human placenta, i.e. amnion and chorion-decidua. Purification of the enzymes was achieved by the freezing-thawing technique, ammonium sulphate fractionation and Sephadex gel filtration. Cathepsis B1 separated either from amnion or from chorion-decidua exhibited optimum activity at pH 6.2
|
695738ad-a8bc-420c-ab52-5efaf3f60154
| 1 |
, and an optimum temperature between 42-45 degrees C. They were inhibited by heavy metals, and compounds which react with the thiol groups. Isoelectric focusing demonstrated three isoenzymes of cathepsin B1 originating from chorion-decidua, while only one band was found for the enzyme from amnion.
|
c776d69a-6b2a-4998-b3ad-bd0d3e71669d
| 0 |
Purification of multiple forms of adenosine deaminase from rabbit intestine. Two forms of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4), differing in molecular size, have been purified and obtained in homogeneous form from rabbit intestine. The purification procedures involved extraction with acetate buffer, pH 5.5, precipitation and fractional reextraction with (NH4)2SO4, ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephadex G-75 and Sephadex G-200.
|
c776d69a-6b2a-4998-b3ad-bd0d3e71669d
| 1 |
Gel filtrations analysis gave molecular weight estimates of 265 000 and 32 000 for the large and small deaminases respectively. The two enzymes forms had similar pH optima and pH stability ranges.
|
f4b70bf1-c14c-47eb-b271-0d7319025548
| 0 |
Stimulation of photosystem I-induced oxidation of chloroplast cytochrome b-559 by pre-illumination and by low pH. (1) The proportion of higher plant chloroplast cytochrome b-559 oxidizable during illumination by low intensity 732 nm light increases as the pH is decreased below 6.5. At pH 5.0-5.3
|
f4b70bf1-c14c-47eb-b271-0d7319025548
| 1 |
total oxidation is seen and subsequent red light can cause reduction of up to 2/3 of the oxidized cytochrome. The oxidation by far red light at pH 5 is inhibited by 2 muM 2,5-dibromo-3-methyl-6-isopropyl-rho-benzoquinone whereas the red light-induced reduction is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea.
|
f4b70bf1-c14c-47eb-b271-0d7319025548
| 2 |
In this pH range ferricyanide-oxidized cytochrome b-559 exists in a form not reducible by ferrocyanide. (2) An increase in the amplitude of far-red induced oxidation also occurs at higher pH (up to pH 7.8) after pre-treatment of chloroplasts with substantially higher levels of light (approx.
|
f4b70bf1-c14c-47eb-b271-0d7319025548
| 3 |
10(6) ergs-cm-2-s-1). The degree of light activation is pH dependent, being more pronounced at lower pH. After light activation, cytochrome b-559 can be completely oxidized by far-red light in a manner reversible by red light up to pH values of 6, and the curve describing the amplitude of far-red oxidation as a function of pH is shifted by 0.5
|
f4b70bf1-c14c-47eb-b271-0d7319025548
| 4 |
-1.0 pH unit toward higher pH. Far-red oxidation and red light reduction are again inhibited by 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, respectively. (3) Light activation at pH 5.2-6.0 is also manifested in a small decrease in the amplitude of subsequent dark ferrocyanide reduction, and this decrease is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (10 muM).
|
f4b70bf1-c14c-47eb-b271-0d7319025548
| 5 |
(4) The effect of intramembranal acidity on the effective redox potential of cytochrome b-559 and its function is discussed.
|
3cf74a52-f324-41a8-a101-8e62429fba5b
| 0 |
The effect of formate on cytochrome aa3 and on electron transport in the intact respiratory chain. 1. Formate inhibits cytochrome c oxidase activity both in intact mitochondria and submitochondrial particles, and in isolated cytochrome aa3. The inhibition increases with decreasing pH, indicating that HCOOH may be the inhibitory species.
|
3cf74a52-f324-41a8-a101-8e62429fba5b
| 1 |
2. Formate induces a blue shift in the absorption spectrum of oxidized cytochrome aa3 (a3 + a33+) and in the half-reduced species (a2 + a33+). Comparison with cyanide-induced spectral shifts, towards the red, indicates that formate and cyanide have opposite effects on the aa3 spectrum, both in the fully oxidized and the half-reduced states.
|
3cf74a52-f324-41a8-a101-8e62429fba5b
| 2 |
The formate spectra provide a new method of obtaining the difference spectrum of a32+ minus a33+, free of the difficulties with cyanide (which induces marked high leads to low spin spectral shifts in cytochrome a33+) and azide (which induces peak shifts of cytochrome a2+ towards the blue in both alpha- and Soret regions).
|
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