Ohno M, Sato S, Mizoguchi H, Tsukamoto S
J Biochem. 1975 Jun;77(6):1341-3.
Steady state kinetic studies of alpha-chymotrypsin [EC 3.4.21.1]-catalyzed hydrolysis of nucleus-substituted derivatives of the specific substrates were made at pH 6.5 and 7.8. Ac-Trp(NCps)-OMe was hydrolyzed more readily than Ac-Trp-OMe owing to its smaller Km value. The kcat values of Ac-Trp(CHO)-OMe and Ac-Tyr(3-no2)-ome were higher than those of the corresponding unmodified substrates, suggesting that derivatives with a substituent as large as a formyl or nitro group at the epsilon-position are stereochemically favorable to the catalytic process. Derivatives of Ac-Phe-OMe with a chain of four atoms at the 3 or 4-position of the phenyl nucleus and 2,3-dihydropyrrolo[2,3-b]indoles derived from Ac-Trp-OMe were not hydrolyzed at all.
在pH 6.5和7.8条件下，对α-胰凝乳蛋白酶[EC 3.4.21.1]催化特定底物的核取代衍生物水解进行了稳态动力学研究。由于其Km值较小，Ac-Trp(NCps)-OMe比Ac-Trp-OMe更容易水解。Ac-Trp(CHO)-OMe和Ac-Tyr(3-no2)-ome的kcat值高于相应的未修饰底物，这表明在ε-位具有与甲酰基或硝基一样大的取代基的衍生物在立体化学上有利于催化过程。在苯核的3或4位带有四个原子链的Ac-Phe-OMe衍生物以及由Ac-Trp-OMe衍生的2,3-二氢吡咯并[2,3-b]吲哚根本不被水解。
