Enzymatic reduction of alkyl and acyl derivatives of dihydroxyacetone phosphate by reduced pyridine nucleotides.

The reductions of either acyl or alkyl derivatives of dihydroxyacetone phosphate by enzymes from ascites tumor cell microsomes with NADPH were studied. The reaction rate was measured by determining the formation of labeled lipid from [4-3H]NADPH. The products were characterized as either 1-acyl or 1-alkyl [2-3H]glycerol d-phosphate formed from the corresponding keto derivatives. The enzymes were found to be distributed in both mitochondrial and microsomal fractions obtained from different organs, i.e. brain, liver, kidney, etc. When [4-3H]NADH was substituted for ]4-3H]NADPH, very little formation of labeled lipid from the dihydroxyacetone phosphate derivatives was observed, showing that the enzymes are specific for NADPH as the coenzyme. The same results were obtained when the reduction was studied with nonradioactive NADH or NADPH and 32P-labeled acyl or alkyl dihydroxyacetone phosphate. Experiments with A-[4-3H]NADPH and B-[4-3H]NADPH proved that only the B-hydrogen from the nicotinamide ring was transferred to reduce the keto compounds. Some preliminary results indicated that one enzyme may be responsible for the reduction of both acyl and alkyl derivatives of dihydroxyacetone phosphate.