Acyl dihydroxyacetone phosphate: precursor of alkyl ethers.

1-0-Alkyl dihydroxyacetone phosphate is biosynthesised in guinea pig liver mitochondria and in rat brain microsomes by direct reaction of a long chain alcohol and acyl dihydroxyacetone phosphate. ATP and Mg* are stimulatory but coenzyme A is not necessary for the reaction. 1-0-Alkyl dihydroxyacetone phosphate (alkyl DHAP)l was shown to be biosynthesized from long chain alcohol and DHAP with ATP, CoA, Mg -I+ and NaF as necessary cofactors (1,2). The requirement of CoA was surprising because the formation of a thioester intermediate could not easily be envisioned. Various preincubation and kinetic studies indicated that an intermediate containing DHAP was a precursor of alkyl DHAP (3). In this report evidence is presented that acyl DHAP, a lipid known to be formed in the same preparations that can form alkyl ethers, reacts with the long chain alcohol to form alkyl DHAP. CoA is needed only for the formation of acyl DHAP from endogenous fatty acid (4). Formation of acyl DHAP in the alkyl DHAP synthesizing enzyme systems has already been reported (1). MATERIALS AND METHODS l-C14-Hexadecanol was prepared by reducing the methyl ester of 1-C 14 palmitate by RED-Al [sodium bis (2-methoxy ethoxy)-aluminum hydride, Aldrich, Milwaukee, Wise.]. 32 P-Labeled palmitoyl DHAP was prepared biosynthetically by incubating palmitate and 32 P-DHAP with guinea pig liver mitochondria and necessary cofactors (4). The labeled lipid was purified by chromatography on silicic acid. 32 P-Acyl GP was prepared by reducing 32 P-acyl DHAP with NaBH4 1 Abbreviations used: DHAP dihydroxyacetone phosphate; GP glycerol-3phosphate.