JBC, Vol. 252, Issue 10, 3459-3459, May, 1977
Overall mechanism and rate equation for O-acetylserine sulfhydrylase
P. F. Cook and R. T. Wedding
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.