In enzymology, an O-acetylhomoserine aminocarboxypropyltransferase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are O-acetyl-<small>L</small>-homoserine and methanethiol, whereas its two products are <small>L</small>-methyionine and acetate.
This enzyme belongs to the family of transferases, specifically those transferring aryl or alkyl groups other than methyl groups. The systematic name of this enzyme class is O-acetyl-<small>L</small>-homoserine:methanethiol 3-amino-3-carboxypropyltransferase. Other names in common use include O-acetyl-<small>L</small>-homoserine acetate-lyase (adding methanethiol), O-acetyl-<small>L</small>-homoserine sulfhydrolase, O-acetylhomoserine (thiol)-lyase, O-acetylhomoserine sulfhydrolase, and methionine synthase. This enzyme participates in methionine metabolism and cysteine metabolism.