Phospholipids chiral at phosphorus. Synthesis of chiral phosphatidylcholine and stereochemistry of phospholipase D

Chirally labeled 1,2-dipalmitoyl-sn-glycero-3-phosphocholines (DPPC) with known configuration were synthesized by N-methylation of chirally labeled 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE). Transphosphatidylation of (RP)- and (SP)-18ODPPC catalyzed by phospholipase D from cabbage gave (RP)- and (SP)-18ODPPE, respectively, as indicated by 31P nuclear magnetic resonance (NMR) analysis of 18ODPPE. Therefore, phospholipase D catalyzes transphosphatidylation with overall retention of configuration at phosphorus. The steric course of hydrolysis of DPPC catalyzed by the same enzyme was elucidated by the following procedures. Hydrolysis of (RP)-17O, 18ODPPC by phospholipase D gave 1,2-dipalmitoyl-sn-glycero-3- 16O , 17O, 18Ophosphate ( 16O , 17O, 18O DPPA ) with unknown configuration. The latter compound was then converted to 1- 16O , 17O, 18Ophospho-(R)-propane-1,2-diol by a procedure involving no P-O bond cleavage Bruzik , K., & Tsai, M.-D. (1984) J. Am. Chem. Soc. 106, 747-754. The configuration of the phosphopropane -1,2-diol was determined as RP by 31P NMR analysis following ring closure and methylation Buchwald , S. L., & Knowles, J. R. (1980) J. Am. Chem. Soc. 102, 6601-6603. The results indicated that hydrolysis of DPPC catalyzed by phospholipase D also proceeds with retention of configuration at phosphorus. Our results therefore support a two-step mechanism involving a phosphatidyl-enzyme intermediate in the reactions catalyzed by phospholipase D from cabbage.