Abstract

31P NMR chemical shifts of the internal aldimine and the cx.-aminoacrylate intermediate of 0- acetylserine sulfhydrylase were determined and found to be 5.13 and 3.95 ppm, respectively. In addition, the line width decreases upon addition of OAS, suggesting a less restricted rotation around the CS'-0 bond of pyridoxal 5' -phosphate in the cx.-aminoacrylate intermediate The upfield shift of the cx.-aminoacrylate is similar to the behavior of the L-serine external Schiff base and may be interpreted as a loosening of the active site.