Ohno M, Karasaki Y
J Biochem. 1979 Nov;86(5):1269-74. doi: 10.1093/oxfordjournals.jbchem.a132642.
Presteady state and steady state analyses of the alpha-chymotrypsin [EC 3.4.21.1]-catalyzed hydrolysis of three specific ester substrates and three ring-substituted derivatives were carried out to elucidate the effect of hydrophobic interactions due to the different side chains of the substrates on the individual steps of the reaction. Hydrolysis of all the substrates except for N alpha-acetyl-Nin-formyltryptophan methyl ester (Ac-Trp(CHO)-OMe) was controlled by the deacylation rate. In spite of their comparable Ks values, the substrates with small kcat, such as N alpha-acetyltryptophan methyl ester and N alpha-acetyl-2-(2-nitro-4-carboxyphenylsufenyl)-tryptophan methyl ester, characteristically gave Km values one order of magnitude smaller than the others. For the reaction of Ac-Trp(CHO)-OMe, it was ascertained that the deacylation step was not rate-controlling. It is suggested that the acylation step controls the rate in this case.
对α-胰凝乳蛋白酶[EC 3.4.21.1]催化三种特定酯底物及三种环取代衍生物水解的预稳态和稳态进行了分析，以阐明由于底物不同侧链导致的疏水相互作用对反应各个步骤的影响。除Nα-乙酰基-N-甲酰基色氨酸甲酯（Ac-Trp(CHO)-OMe）外，所有底物的水解均受脱酰化速率控制。尽管它们的Ks值相当，但kcat较小的底物，如Nα-乙酰基色氨酸甲酯和Nα-乙酰基-2-(2-硝基-4-羧基苯磺酰基)-色氨酸甲酯，其特征是Km值比其他底物小一个数量级。对于Ac-Trp(CHO)-OMe的反应，已确定脱酰化步骤不是速率控制步骤。建议在这种情况下酰化步骤控制速率。
