Catalyzes the production of homocysteine from O-acetylhomoserine (OAH) and hydrogen sulfide (H2S), a step in the methionine biosynthesis pathway. Is not able to form cystathionine from O-acetylhomoserine and L-cysteine. hydrogen sulfide + O-acetyl-L-homoserine = acetate + L-homocysteine Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homocysteine from O-acetyl-L-homoserine: step 1/1. Belongs to the trans-sulfuration enzymes family.