Inhibition of glycerol-3-phosphate acyltransferase by analogs of glycerol-3-phosphate

Analogs of glycerol-3-phosphate were tested as substrates or inhibitors of the glycerol-3-phosphate acyltransferases of mitochondria and microsomes. (rac)-3,4-Dihydroxybutyl-1-phosphonate, (rac)-glyceraldehyde 3-phosphate, (rac)-3-hydroxy-4-oxobutyl-1-phosphonate, (1S,3S)-1,3,4-trihydroxybutyl-1-phosphonate, and (1R,3S)-1,3,4 trihydroxybutyl-1-phosphonate were competitive inhibitors of both mitochondrial and microsomal sn-glycerol-3-phosphate acyltransferase activity. An isosteric analog of dihydroxyacetone phosphate, 4-hydroxy-3-oxobutyl-1-phosphonate, was a much stronger competitive inhibitor of the microsomal than the mitochondrial enzyme. Phenethyl alcohol was a noncompetitive inhibitor of both the microsomal and the mitochondrial acyltransferases. The product of the mitochondrial acyltransferase reaction with (rac)-3,4-dihydroxybutyl-1- phosphonate was almost exclusively (rac)-4-palmitoyloxy-3-hydroxybutyl-1-phosphonate. The microsomal acylation reaction generated both the monoacyl product and (S)-3,4-dipalmitoyloxybutyl-1-phosphonate. The apparent Km for (S)-3,4-dihydroxybutyl-1-phosphonate was 2.50 and 1.38 mM for the mitochondrial and microsomal enzymes, respectively.