Sulfur amino acid metabolism in<i>Schizosaccharomyces pombe</i>: occurrence of two<i>O</i>-acetylhomoserine sulfhydrylases and the lack of the reverse transfulfuration pathway

Abstract

The fission yeast Schizosaccharomyces pombe has a unique organization of sulfur amino acid metabolism: it has two distinct O-acetylhomoserine sulfhydrylases (homocysteine synthases). Similar to Enterobacteriaceae, S. pombe lacks cystathionine beta-synthase and cystathionine gamma-lyase-the enzymes of the reverse transsulfuration pathway, by which methionine is readily metabolized to cysteine-a likely effector in the sulfur metabolite repression system. Consequently no repression of sulfate assimilation is observed when methionine is added to the growth medium.