Cook P F, Wedding R T
J Biol Chem. 1977 May 25;252(10):3459.
Saturation curves for O-acetylserine sulfhydrylase using the substrate analogues O-propionyl-L-serine, O-butyryl-L-serine, and beta-chloro-L-alanine all exhibit substrate inhibition and yield Km values comparable to O-acetyl-L-serine, except the O-butyryl derivative which has a Km 5-fold higher. Since all analogues are used as substrates and yield similar kinetic parameters in most cases, it is possible that they share a common intermediate. This evidence also suggests that specificity of O-acetylserine sulfhydrylase resides in the fact that the beta-substituted moiety on L-serine is a good leaving group. The overall rate equation for O-acetylserine sulfhydrylase was derived. A comparison of the numerical integration of the rate equation and an experimental time course is given.
使用底物类似物O-丙酰基-L-丝氨酸、O-丁酰基-L-丝氨酸和β-氯-L-丙氨酸的O-乙酰丝氨酸巯基酶的饱和曲线均表现出底物抑制作用，并且除了Km值高5倍的O-丁酰基衍生物外，其余衍生物产生的Km值与O-乙酰-L-丝氨酸相当。由于所有类似物都用作底物，并且在大多数情况下产生相似的动力学参数，因此它们可能共享一个共同的中间体。这一证据还表明，O-乙酰丝氨酸巯基酶的特异性在于L-丝氨酸上的β-取代部分是一个良好的离去基团。推导了O-乙酰丝氨酸巯基酶的总体速率方程。给出了速率方程的数值积分与实验时间进程的比较。
