Protein
Homocysteine/cysteine synthase
Organism
Saccharomyces cerevisiae (strain ATCC 204508 / S288c)
Function
Catalyzes the conversion of O-acetyl-L-homoserine (OAH) into homocysteine in the methionine biosynthesis pathway. Also catalyzes the conversion of O-acetylserine (OAS) into cysteine, the last step in the cysteine biosynthesis pathway (PubMed:7765825, PubMed:4609980, PubMed:795806). However, it seems that in S.cerevisiae cysteine biosynthesis occurs exclusively through the cystathionine pathway and not via direct incorporation of sulfur into OAS (PubMed:1732168). It therefore has no metabolic role in cysteine biosynthesis and may only have a regulatory role controlling OAS levels (PubMed:12586406).
Similarity
Belongs to the trans-sulfuration enzymes family.
Sequence
MPSHFDTVQLHAGQENPGDNAHRSRAVPIYATTSYVFENSKHGSQLFGLEVPGYVYSRFQNPTSNVLEERIAALEGGAAALAVSSGQAAQTLAIQGLAHTGDNIVSTSYLYGGTYNQFKISFKRFGIEARFVEGDNPEEFEKVFDERTKAVYLETIGNPKYNVPDFEKIVAIAHKHGIPVVVDNTFGAGGYFCQPIKYGADIVTHSATKWIGGHGTTIGGIIVDSGKFPWKDYPEKFPQFSQPAEGYHGTIYNEAYGNLAYIVHVRTELLRDLGPLMNPFASFLLLQGVETLSLRAERHGENALKLAKWLEQSPYVSWVSYPGLASHSHHENAKKYLSNGFGGVLSFGVKDLPNADKETDPFKLSGAQVVDNLKLASNLANVGDAKTLVIAPYFTTHKQLNDKEKLASGVTKDLIRVSVGIEFIDDIIADFQQSFETVFAGQKP