Involved in the biosynthesis of the antibiotic D-cycloserine (DCS), a cyclic structural analog of D-alanine, used as an antitubercular agent. Catalyzes the transfer of the acetyl group from acetyl-CoA to the hydroxyl group of L-serine to yield the activated serine, O-acetyl-L-serine. It prefers L-serine over L-homoserine. acetyl-CoA + L-serine = CoA + O-acetyl-L-serine acetyl-CoA + L-homoserine = CoA + O-acetyl-L-homoserine kcat is 95 min(-1) and 88 min(-1) for L-serine and L-homoserine, respectively (at 30 degrees Celsius and pH 8). Antibiotic biosynthesis. Homodimer. Belongs to the AB hydrolase superfamily. MetX family.