SUBCELLULAR-DISTRIBUTION OF O-ACETYLSERINE(THIOL)LYASE IN CAULIFLOWER(BRASSICA-OLERACEA L) INFLORESCENCE

The subcellular localization of O-acetylserine(thiol)lyase (EC 4.2.99. 8) in nongreen tissue from higher plants has been studied using purifi ed proplastids, mitochondria, and protoplasts from cauliflower (Brassi ca oleracea L.) buds as a source of subcellular fractions. O-Acetylser ine(thiol)lyase has been detected in both organelles (proplastids and mitochondria) and a cytosolic extract obtained by protoplast fractiona tion. We confirmed these observations, demonstrating that a form of th e enzyme different in global charge and separated from others by anion -exchange chromatography corresponded to each subcellular location. Ou r observations are consistent with the need for cysteine biosynthesis in each subcellular compartment where the synthesis of proteins occurs .