共查询到20条相似文献,搜索用时 15 毫秒
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The isolation of N-acetyl-L-tryptophanyl- -chymotrypsin 总被引:1,自引:0,他引:1
A L Fink 《Archives of biochemistry and biophysics》1973,155(2):473-474
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L D Faller 《The Journal of biological chemistry》1971,246(24):7446-7453
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Urea denaturation of active-site spin-labeled -chymotrypsin 总被引:1,自引:0,他引:1
L J Berliner 《Biochemistry》1972,11(15):2921-2924
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A. Previero F. Kraicsovits M. Pugnière M A. Coletti-Previero 《Biotechnology letters》1981,3(10):571-576
Summary Chymotrypsin catalyses the hydrolysis of the D-isomers of aromatic amino acids and of glycine methyl esters provided that pyridoxal is present. The corresponding L-isomers still behave as substrates for the enzyme even if pyridoxal decreases the rate of their hydrolysis. This change of enzyme stereospecificity should be taken into account in biotechnological processes. 相似文献
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The concentration-dependent self-association of α-chymotrypsin is known to be influenced by various factors including the
presence of small molecules and autolysis products. In this connection the effect of various amino acids on the self-association
of α-chymotrypsin has been studied, as a point of interest, by measuring the sedimentation coefficient of α-chymotrypsin.
The influence of an amino acid is seen to be governed by the nature of its side chain. Some amino acids do not affect the
self-association of α-chymotrypsin at all while some affect it moderately and some others considerably. Functional groups
such as the - OH group of Ser or the phenolic ring of Tyr do not seem to influence self-association behaviour. Based on these
effects, amino acids could be categorized into 3 groups. Activity studies in the presence of amino acids indicate that the
site of self-association and the active-site are probably mutually exclusive. 相似文献
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Yasuko Kawamura Kazuhiro Nakanishi Ryuichi Matsuno Tadashi Kamikubo 《Biotechnology and bioengineering》1981,23(6):1219-1236
The thermal of free and immobilized α-chymotrypsin was investigated experimentally and theoretically. The inactivation process of free α-chymotrypsin was analyzed with a kinetic model which included a first- order reaction process and autolysis. The effects of ionic strength, Ca2+ concentration, and temperature are discussed here in terms of the estimated kinetic parameters included in this model. The inactivation process of α-chymotrypsin immobilized onto various supports by several methods was investigated. The Contribution of thermal denaturation and autolysis to the inactivation depended upon the method of immobilization. To interpret quantitatively the non-first-order thermal denaturation process of the immobilized enzyme, a model in which the heterogeneity of the immobilized enzyme was taken into account is proposed. 相似文献
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Native α-chymotrypsin (N-Chtr) and two modified forms, methionine-192 sulfoxide (O-Chtr) and methionine-192-S-(N-2-carboxyisopropyl)carbamylmethyl (Al-Chtr) α-chy-motrypsin have been compared in hydrolysis of methyl β-phenylpropionate and its d-and l-α-substituted derivatives, in which substituents are Cl, OH, OCOCH3, NHCHO, and NHCOCH3. In general, both modifications lower the reactivity of the enzymes in terms of kcat and Km(app); the decrease is greater toward l than toward d-enantiomers, and stereoselectivity is decreased. It is proposed that the modifications change the methionine-192 side chain from hydrophobic to hydrophilic, bring it into solution, and enlarge the Met-192-Ser-214 passage in which α-substituents fit. This leads to weaker binding, allows more freedom of motion of substrates and decreases reactivity, while allowing easier access of d-α-substituents. The large modifying substituent of Al-Chtr counters this effect by steric interaction with the large d-α-acetoxy and d-α-acylamido substituents, while the small polar modification in O-Chtr favors hydrolysis of these d-substrates. 相似文献
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Sedimentation equilibrium experiments indicate that neither human chymotrypsin II nor bovine δ-chymotrypsin molecules undergo association in the pH range 3–5 where dimerization occurs with α-chymotrypsin. The weight-average molecular weights of human chymotrypsin II and δ-chymotrypsin in a pH 4.4 0.1 ionic strength buffer are 26,200 and 26,400, respectively, using the measured partial specific volumes of 0.722 and 0.727 ml/g at 25 °C. Number-average molecular weight calculations also support the presence of monomeric species at this pH. In the pH range 6–7.6 where sedimentation velocity studies have shown that δ-chymotrypsin associates at concentrations above 3 mg/ml, no association was observed for either the human chymotrypsin II or bovine δ-chymotrypsin in the sedimentation equilibrium experiments where protein concentrations were below 1.2 mg/ml. These studies provide additional evidence that human chymotrypsin II is similar to bovine δ-chymotrypsin. 相似文献