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1.
《The International journal of biochemistry》1992,24(10):1657-1660
- 1.1. A thermostable orthophosphoric monoester phosphohydrolase (EC 3.1.3.1) from Thermus sp strain Rt41A has been purified 400-fold to give a specific activity of 25 U/mg at 60°C in IM diethanolamine (pH 11.1).
- 2.2. The enzyme has a Mr of 160,000 and is trimeric.
- 3.3. The half-life of the enzyme is 5 min at 85°C.
- 4.4. The enzyme has a wide specificity for a number of phosphate monoesters.
- 5.5. The Hm of the enzyme is pH dependent, so the pH optimum of the enzyme is affected by the substrate concentration.
- 6.6. The enzyme is inhibited 50% by 20 mM Ca2+ or Mg2+.
- 7.7. The Ki for phosphate, EDTA-di sodium salt and arsenate (in 1 M diethanolamine, pH 11.1) is approx 1.2, 1.6 and 4mM respectively.
- 8.8. Urea (200 mM) is not inhibitory.
2.
《Comparative biochemistry and physiology. C: Comparative pharmacology》1988,89(2):399-402
- 1.1. Optimum in vitro conditions, and kinetics of the enzyme catechol-O-methyltransferase from the brain of the male African catfish were studied.
- 2.2. A saturated level for S-adenosylmethionine, as methyldonor, and magnesium as cofactor was reached at 5 μM and 10 mM, respectively.
- 3.3. The addition of ascorbic acid, as an antioxidant, and tranylcypromine, as a MAO inhibitor, was not necessary, during incubations with fore-brain homogenates.
- 4.4. Kinetic analysis of the methylation of catecholestrone, catecholestradiol and dopamine showed Km values of 1.2, 0.6 and 0.5 μM, respectively.
- 5.5. The affinity of the catecholsubstrates for the enzyme catechol-O-methyltransferase is much higher in the brain of the African catfish than in tissues of mammals.
3.
《The International journal of biochemistry》1988,20(4):463-470
- 1.1. Partially purified rat liver ornithine decarboxylase is inhibited by several diamines including putrescine, 1,3-diaminopropane, cadaverine and p-phenylenediamine.
- 2.2. The inhibition is dependent on pH, being strong at pH above 8 and negligible below pH 6.5.
- 3.3. The kinetic study of the inhibition showed that while the aromatic diamine behaved as a simple competitive inhibitor, the aliphatic diamines presented a more complex pattern of inhibition in which two molecules of inhibitor might bind to the enzyme active site.
- 4.4. The KI values for the different inhibitors were calculated and the degree of affinity for the enzyme was p-phenylenediamine > putrescine > cadaverine > 1,3-diaminopropane.
- 5.5. A molecular mechanism explaining how one or two molecules of inhibitor can bind to the enzyme is proposed.
4.
《The International journal of biochemistry》1993,25(8):1157-1164
- 1.1. A proteinaceous inhibitor for S-adenosyl-l-methionine (AdoMet)-dependent transmethylation reactions has been purified to apparent homogeneity from rat liver cytosolic fraction.
- 2.2. The peptide was made up of 29 amino acid residues with a molecular weight of 2,584. Glycine accounted for 52% of the total amino acids.
- 3.3. Employing AdoMet: protein-carboxyl O-methyltransferase (Protein methylase II) and bovine serum γ-globulin as in vitro substrate, the mode of inhibition was found to be non-competitive with Ki value of 1.9 × 10−8 M.
- 4.4. When the inhibitor was present in the reaction mixture together with S-adenosyl-l-homocysteine (AdoHcy), which is a competitive inhibitor for AdoMet, the extent of inhibition exceeded that exerted by each individual inhibitor alone, suggesting that the sites of the inhibitors on the enzyme molecule are different.
- 5.5. Almost a stoichiometric relationship exists between the enzyme and the inhibitor molecule, the ratio being approx one.
5.
《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,86(3):851-854
- 1.1. The glyoxylic acid cycle pathway could be regulated through the modulation of the isocitrate dehydrogenase-NADP activity. This enzyme is inhibited by NADPH.
- 2.2. The effect on the glyoxylate cycle flux of variations in the rate of the NADPH-consuming pathways has been studied.
- 3.3. Increase in the rate of NADPH-consuming activity by addition of H2O2 produces inhibition of the glyoxylate cycle and decrease in the NADPH/NADP ratio.
- 4.4. These results suggest that the glyoxylate flux in Tetrahymena could be modulated by regulation of NADP-dependent isocitrate dehydrogenase by the NADPH/NADP ratio.
6.
《The International journal of biochemistry》1987,19(9):831-835
- 1.1. Malic enzyme purified from the fruit tissue of Mangifera indica was irradiated in dilute solution and the effect of γ-irradiation was investigated.
- 2.2. The activity of the enzyme decreased exponentially as a function of the applied dose under all conditions investigated. The inactivation yield (Go-value) in neutral solution and in air was 0.069.
- 3.3. The role of the radicals produced by water radiolysis in the inactivation of the enzyme was investigated by using different gas atmospheres and selective free radical-anions. The hydrogen atom and the hydrated electron (reducing species) were found to be important in the enzyme inactivation; as well as the possible destruction of cysteine and tryptophan residues.
- 4.4. The irradiated enzyme appears to adopt a more compact conformation as reflected in a slightly lower Mr, Stokes-radius and diffusion coefficient.
- 5.5. γ-Radiation does not lead to any heterogeneity in the charge and size properties of the enzyme and the pI and the Mr of the subunits were unaffected.
- 6.6. Some differences in the amino acid composition of the non-irradiated and irradiated enzyme were observed but specific amino acid residues were not preferentially destroyed.
- 7.7. These changes were also reflected in the ultraviolet spectrum of the enzyme which shifted to lower values.
- 8.8. The major cause of inactivation seem to be a change in conformation caused by chemical modification of amino acid side chains.
7.
《Comparative biochemistry and physiology. B, Comparative biochemistry》1981,68(1):147-151
- 1.1. An acid RNase was purified 620-fold from the roe of the fish Cyprinus carpio L. The recovery was 12.4% and the enzyme appeared to be homogenous as judged by the SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE).
- 2.2. The enzyme displays maximum activity at pH 5.50, I = 50 mM and the mol. wt is 22,000.
- 3.3. The purified enzyme shows two molecular forms (pI1 = 4.04, pI2 = 4.75) as revealed by the isoelectric focusing technique.
- 4.4. The enzyme hydrolyses both Poly(A) and Poly(U) showing a stronger preference for Poly(U), Neither Poly(G) nor Poly(C) was hydrolysed.
8.
《The International journal of biochemistry》1984,16(1):117-120
- 1.1. The specific activity of GMP synthetase was measured in several human tissues and found to be highest in cultured skin fibroblasts, followed by bone marrow, leukocytes, erythrocytes. placenta, and liver.
- 2.2. The enzyme from fibroblasts was purified approximately 50-fold by ammonium sulfate fractionation and gel filtration.
- 3.3. The Km values were determined to be 4.9μM for XMP, 270μM for ATP. and 340 μM for glutamine.
- 4.4. Ammonium sulfate could replace glutamine as the amino donor but was much less efficient.
- 5.5. The enzyme was specific for ATP as the energy source.
- 6.6. Unlike the calf thymus enzyme, the human enzyme has no requirement for a reduced sulfhydryl compound.
- 7.7. Human GMP synthetase is inhibited by ATP, dATP, azaserine, and hydroxylamine.
9.
《The International journal of biochemistry》1984,16(11):1099-1106
- 1.1. NAD(P)H dehydrogenase from rabbit liver was purified to electrophoretic homogeneity using a procedure also found applicable for the rat liver enzyme.
- 2.2. Rabbit and rat liver enzymes showed different behaviour in isoelectric focusing and different Km values and turnover numbers.
- 3.3. Both enzymes were inhibited to similar extents by warfarin.
- 4.4. The rabbit enzyme is composed of two subunits of mol. wt 27,000 and contained 1 FAD group per subunit.
- 5.5. Some absorption and circular dichroism properties of the rat enzyme are shown.
10.
《The International journal of biochemistry》1993,25(6):879-884
- 1.1. Phospholipase A2 was isolated from Agkistrodon bilineatus venom by Sephadex G-75 and CM-Cellulose column chromatographies.
- 2.2. The purified phospholipase A2-I gave a single band on disc polyacrylamide gel electrophoresis, isoelectric focusing and sodium dodecyl sulfate polyacrylamide gel electrophoresis.
- 3.3. The enzyme preparation had a molecular weight of 14,000, isoelectric point of pH 8.77 and possessed 123 amino acid residues.
- 4.4. The purified phospholipase A2 possessed lethal, indirect hemolytic and anticoagulant activities.
- 5.5. The enzyme hydrolyzed the phospholipids phosphatidyl choline (PC), phosphatidyl ethanolamine (PE), phosphatidyl inositol (PI) and phosphatidyl serine (PS).
- 6.6. The concentration of mouse diaphragm was inhibited and the contraction of guinea pig left atrium was increased by phospholipase A2-I.
- 7.7. Phospholipase A2 activity of this preparation was inhibited by ethylenediamine tetraacetic acid, p-bromo phenacyl bromide, n-bromo succinimide or dithiothreitol, but not by diisopropyl fluorophosphate or benzamidine.
11.
《Comparative biochemistry and physiology. B, Comparative biochemistry》1978,59(2):247-252
- 1.1. Lipoamide dehydrogenase was purified 1500-fold from mackerel dark muscle.
- 2.2. The enzyme was homogeneous as judged by acrylamide gel electrophoresis in the presence and absence of SDS.
- 3.3. Molecular weights of 102,000 and 55,000 were estimated for the native and denatured enzyme, respectively.
- 4.4. Optimal activity for the enzyme was obtained at around pH 5.7 and enhanced with citri acid.
- 5.5. Loss of activity was less than 5% by incubating the enzyme at 70°C for 20 min.
- 6.6. An apparent Km of 3.1 × 10−3 M was obtained for dl-lipoic acid and 1.5 × 10−5 M for NADH.
- 7.7. The properties of lipoamide dehydrogenase from mackerel dark muscle observed in this investigation were very similar to those reported for the enzyme from other sources.
12.
《Comparative biochemistry and physiology. B, Comparative biochemistry》1980,65(1):155-158
- 1.1. Physalia physalis nematocyst venom contains a DNase which has a non-specific endonucleolytic action.
- 2.2. This enzyme has an approximate molecular weight of 75,000 daltons.
- 3.3. The enzyme can cleave DNA over a wide pH range with an optimum near neutrality.
- 4.4. The enzyme is thermolabile and its activity can be stimulated by 80 nM NaCl or 10 mM MgCl2.
13.
《Comparative biochemistry and physiology. A, Comparative physiology》1986,83(3):489-493
- 1.1. Fundamental chitin digestion characteristics of Crassostrea virginica crystalline style were investigated.
- 2.2. Optimum temperature and pH were 34°C and 4.8. respectively.
- 3.3. The colloidal regenerated chitin (0.56mol/0.5 ml: GlcNAc equivalents) was saturating under all enzyme levels encountered.
- 4.4. There was no evidence of end product inhibition, even after 100 hr incubation.
- 5.5. Calculated Km for the chitinase complex was 1.19mM when determined using a 30 min assay, but was only 0.70 mM when determined using a 4.6 hr assay.
- 6.6. Both Km values are lower than reported for similar assays in other molluscs and for most bacteria.
- 7.7. Effect of substrate preparation on the kinetics are discussed.
- 8.8. Eight peaks of chitinase activity were resolved by DEAE-Fractogel ion exchange chromatography.
14.
《The International journal of biochemistry》1991,23(10):991-995
- 1.1. Purified ostrich (Struthio camelus) liver fructose-1,6-bisphosphatase exhibited an absolute requirement for Mg2+.
- 2.2. The enzyme catalyzed the hydrolysis of fructose-1,6-bisphosphate, sedoheptulose-l,7-bisphosphate and ribulose-l,5-bisphosphate.
- 3.3. S0.5 for substrate was 1.4 μM.
- 4.4. AMP was a potent non-competitive inhibitor with respect to substrate (Ki of 25 μM).
- 5.5. Fructose-2,6-bisphosphate was a potent competitive inhibitor of the enzyme (Ki of 4.8 μM).
15.
《The International journal of biochemistry》1989,21(8):909-912
- 1.1. A third form (D3) of cyclic nucleotide phosphodiesterase from Rhizobiumfrediiv/as detected and characterized for the first time.
- 2.2. The enzyme could hydrolyse both cyclic AMP and cyclic GMP with apparent Km for cyclic AMP of approx. 0.2 μM.
- 3.3. D3 cyclic nucleotide phosphodiesterase had a pH optimum of about 6.0 when hydrolysing cyclic AMP.
- 4.4. The enzyme lost almost all its activity when heated to 60°C for 20 min.
- 5.5. Gel filtration with Sephadex G-100 gave a mol. wt of approx. 42.5 kD for the native enzyme.
16.
《Comparative biochemistry and physiology. A, Comparative physiology》1981,68(1):103-106
- 1.1. Healthy 6- to 12-day-old Heliothis zea (bollworm) larvae showed a mean oxygen uptake of 3.1 μl O2/mg body wt per hr.
- 2.2. Similar larvae infected with the fungus Nomuraea rileyi had a mean uptake of 4.01 μl O2/mg per hr.
- 3.3. The weights of the two groups of insects did not differ.
- 4.4. T-test showed a significant (P < 0.01) difference in oxygen uptake between healthy and infected larvae.
17.
《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,86(4):1151-1155
- 1.1. Biliverdin reductase from the liver of eel, Anguilla japonica was characterized and purified with a novel enzymatic staining method on polyacrylamide electrophoretic gel.
- 2.2. This enzyme could use both NADPH and NADH as coenzyme. The Km of NADPH was 5.2 μM, while that of NADH was 5.50 μM.
- 3.3. The optimum reaction pH for using HADPH as coenzyme was 5.3. That for NADH was 6.1. The optimum reaction temperature is 37°C.
- 4.4. When NADPH was used as coenzyme, the Km of biliverdin was 0.6 μM. When NADH was used as coenzyme, the Km of biliverdin was 7.0 μM.
- 5.5. The activity of the enzyme was inhibited by the concentration of biliverdin. Also, the potency of the enzyme was much less than that of the analogous enzyme isolated from mammals.
- 6.6. This is a fairly stable enzyme with a mol. wt around 67,000. Its estimated pI was pH 3.5–4.0.
- 7.7. This is the first time biliverdin reductase has been isolated and characterized from a vertebrate other than mammals. The property of it is quite different from that of mammals.
18.
《The International journal of biochemistry》1991,23(12):1445-1451
- 1.1. An alkaline p-nitrophenylphosphate phosphatase has been purified 440-fold from extracts of Hatobacterium halobium.
- 2.2. The enzyme has an apparent molecular weight of 24,000.
- 3.3. A Km value for p-nitrophenylphosphate of 1.12mM has been found under optimal conditions.
- 4.4. The enzyme is selectively activated and stabilized by Mn2+.
- 5.5. It requires high salt concentrations for stability and maximum activity.
- 6.6. It displays an unusual restricted substrate specificity of 25 phosphate esters tested, only phosphotyrosine and casein were hydrolysed besides p-nitrophenylphosphate.
19.
- 1.1. The role of aldosterone on active potassium transport across lizard colon under voltage-clamped conditions has been investigated.
- 2.2. Control colons exhibited no net potassium flux (Jknet) despite of the existence of active opposite unidi ectional fluxes.
- 3.3. An important net secretory potassium flux was found in short-circuited aldosterone-stimulated colons.
- 4.4. Mucosal amiloride did not change (Jknet) either in control or aldosterone-stimulated colons.
- 5.5. Luminal barium alters K + transport in a manner consistent with the presence of barium-sensitive conductances at the apical membrane of both control and aldosterone-treated colons.
- 6.6. The effects of ouabain and barium on control and aldosterone-induced potassium flows were consistent with a model involving basolateral uptake by an Na +-K +-ATPase and conductive exit across the apical membrane.
- 7.7. The stimulatory effect of aldosterone on potassium secretion is associated with parallel increases of both basolateral K + entry and the apical conductive pathway.
20.
《The International journal of biochemistry》1985,17(3):341-345
- 1.1. A new tetralysine endopeptidase from Escherichia coli AJ005 has been purified about 135-fold.
- 2.2. The peptidase seems to be specific to tetralysine among lysine homopolymers.
- 3.3. The optimal pH was about 7.5
- 4.4. The activity was inhibited by KCN but not inhibited by soybean trypsin inhibitor.
- 5.5. The apparent Km value was 2.5 × 1O−3 M for tetralysine.