猪胃蛋白酶C对小型合成底物的催化活性。
The catalytic activity of pig pepsin C towards small synthetic substrates.
作者信息
Auffret C A, Ryle A P
出版信息
Biochem J. 1979 Apr 1;179(1):239-46. doi: 10.1042/bj1790239.
A series of small peptides has been synthesized and used to investigate the activity of a minor pig pepsin, pepsin C (EC 3.4.23.3). The peptides had the general formula A-Leu-Val-His-B. B was either OMe, NH2 or OH. With B = NH2 hydrolysis (kcat./Km) at 37 degrees C and pH 2.07 increased as A was Ac-Ala, Ac-Tyr, Ac-Phe and Ac-Ala-Phe. The pH dependence of the hydrolysis of Ac-Phe-Leu-Val-His-NH2 indicated the apparent pKa values of two catalytically important groups on the enzyme as 1.42 and 4.88. Inhibition of the hydrolysis of the same peptide by Ac-Phe at pH 3.01 showed a form of mixed non-competitive inhibition. Hydrolysis of Ac-Tyr-Leu-Val-His-OMe and the corresponding amide showed non-classical kinetics, which are discussed in terms of a substrate-activating mechanism. The results are discussed with reference to observations made by other workers on pig pepsin A.
已合成了一系列小肽，并用于研究一种次要的猪胃蛋白酶——胃蛋白酶C（EC 3.4.23.3）的活性。这些肽的通式为A - Leu - Val - His - B。B为OMe、NH₂或OH。当B = NH₂时，在37℃和pH 2.07条件下的水解（kcat./Km）随着A为Ac - Ala、Ac - Tyr、Ac - Phe和Ac - Ala - Phe而增加。Ac - Phe - Leu - Val - His - NH₂水解的pH依赖性表明该酶上两个催化重要基团的表观pKa值分别为1.42和4.88。在pH 3.01时，Ac - Phe对同一肽水解的抑制表现为一种混合非竞争性抑制形式。Ac - Tyr - Leu - Val - His - OMe及其相应酰胺的水解表现出非经典动力学，本文根据底物激活机制对其进行了讨论。结合其他研究人员对猪胃蛋白酶A的观察结果对这些结果进行了讨论。
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