acetyl-CoA + L-serine = CoA + O-acetyl-L-serine Feedback inhibitions by L-Ser and acetyl-CoA. Amino-acid biosynthesis; L-cysteine biosynthesis; L-cysteine from L-serine: step 1/2. Homomultimer. Mostly expressed in stems, flowers and siliques. Localized in vascular tissues, particularly in phloem. By cadmium (Cd). Not induced under sulfur-deficient conditions. Belongs to the transferase hexapeptide repeat family.