Complex Lipid Requirements for Detergent-Solubilized Phosphoacetylmuramyl-Pentapeptide Translocase from Micrococcus luteus

摘要

Phospho-MurNAc-pentapeptide translocase activity in the membrane of M. luteus was lost upon addition of the detergent, Triton X-100, but could be restored by addition of lipid fractions to the assay. By assay in the presence of lipid, the activity of the Triton-solubilized enzyme could be measured. The synthesis of C55-isoprenyl-P-P-MurNAc-pentapeptide from UDP-MurNAc-pentapeptide required C55-isoprenyl-P, and was stimulated by a neutral lipid. The exchange reaction of UDP-MurNAc-pentapeptide with UMP required a polar lipid fraction, but the reaction was not affected by C55-isoprenyl-P or the neutral lipid. Thus, measurement of activity of the detergent-solubilized enzyme requires addition of three lipids, the lipid substrate (C55-isoprenyl-P), the neutral lipid, and a polar lipid.