Partial purification and comparison of some properties of L-serine sulfhydro-lyase of Saccharomyces cerevisiae.

In order to ascertain the role of L-serine sulfhydro-lyase (L-serine hydro-lyase (adding homocysteine) EC 4.2.1.22) which also catalyzes sulfhydrylation of O-acetyl-L-serine (Yamagata, S. (1981) J. Bacteriol. 147, 688-690), the enzyme was partially purified from a wild-type strain and three cysteine auxotrophs of Saccharomyces cerevisiae, and the molecular and enzymatic properties of these preparations were compared. The results showed no significant difference in properties investigated, indicating that cysteine synthesis is exclusively performed in this organism through sulfhydrylation of O-acetyl-L-serine, catalyzed not by serine sulfhydro-lyase but by O-acetylserine . O-acetylhomoserine sulfhydro-lyase (Yamagata, S., Takeshima, K. and Naiki, N. (1974) J. Biochem. 75, 1221-1229). Insensitivity of the former enzyme to L-methionine also supported this conclusion.