BIOCHEMICAL AND BlOPHYSlCAL RESEARCH COMMUNICATIONS BIOSYNTHESIS OF PHOSPHATIDIC ACID FROM DIHYDROXYACETONE PHOSPHATE

Phosphatidic acid is synthesized by a particulate preparation of of guinea pig liver from dihydroxyacetone phosphate, acyl CoAs and NADPH via acyl dihydroxyacetone phosphate. Glycerol-3-phosphate is also converted to phosphatidate in this system. The phosphatidate formed via acyl dihydroxyacetone phosphate has more saturated fatty acid in the lposition than in the Z-position, while the fatty acid distribution in phosphatidate from glycerophosphate is more random. Acyl dihydroxyacetone phosphate was recently characterized by us to occur in guinea pig liver (1) and to be formed biosynthetically by acylation of dihydroxyacetone phosphate (DHAP>* with acyl CoA (2). This lipid is then reduced in mitochondria by NADPH to lysophospbatidate (3). Acylation of lysophosphatidate to phosphatidate (PA)* has been demonstrated (4,5). These reactions, taken together, indicate the presence of an alternate pathway for the biosynthesis of PA from DHAP without its prior reduction to GP (6). Though acylation of GP is known to occur (7), the distribution of fatty acids in the land 2-position of the resulting PA does not correspond to the specific distribution of saturated and unsaturated fatty acids in natural glycerides and phosphoglycerides (8,9). In this report, the formation of PA from DHAP is demonstrated and the fatty acid distribution pattern of the resulting lipid is compared to that derived from GP. Most of the materials and methods were described previously (1,2,3). Lipids from the incubation mixtures were extracted with acidic chloroform-