Role of O‐acetylhomoserine sulfhydrylase in sulfur amino acid synthesis in various yeasts

摘要

AbstractMutants defective in O‐acetylhomoserine sulfhydrylase (OAH‐SHLase) were obtained in five yeast strains representative of different yeast genera:Saccharomyces cerevisiae, Kluyveromyces lactis, Yarrowia lipolytica, Schizosaccharomyces pombeandTrichosporon cutaneum. In vitro, in all five strains, the enzyme also had O‐acetylserine (OAS) sulfhydrylase activity so it is a ‘bifunctional’ OAH/OAS‐SHLase (Yamagata, 1989). The enzyme was only found to be essential inS. cerevisiae(OAH SHLase‐negative mutants are auxotrophs). Its impairment inK. lactiscaused a slower growth rate and a decrease of the sulfur amino acid pool. InT. cutaneumonly the pool was affected whereas inY. lipolyticaandS. pombethe lesion caused no change in the growth rate nor in the pool. In all strains where OAH SHLase‐negative mutants were prototrophs, a monofunctional OAS sulfhydrylase was detected. The results indicate that OAH SHLase may play different physiological roles in