DIFFERENTIAL INFLUENCE OF RAT-LIVER FATTY-ACID-BINDING PROTEIN ISOFORMS ON PHOSPHOLIPID FATTY-ACID COMPOSITION - PHOSPHATIDIC-ACID BIOSYNTHESIS AND PHOSPHOLIPID FATTY-ACID REMODELING

The ability of two rat liver fatty acid binding protein (L-FABP) isofo rms to influence microsomal phosphatidic acid biosynthesis, a key inte rmediate in glycerolipid formation, and phospholipid fatty acid remode ling was examined in vitro, Isoform I enhanced microsomal incorporatio n of [1-C-14]-oleoyl-CoA into phosphatidic acid 7-fold while isoform I I had no effect relative to basal. In contrast, isoform II enhanced mi crosomal incorporation of [1-C-14]-palmitoyl-CoA into phosphatidic aci d 4-fold while isoform I had no effect. These results suggest that eac h L-FABP isoform selectively utilized different acyl-CoAs for glycerol -3-phosphate esterification. Both isoforms stimulated phosphatidic aci d formation by increasing glycerol-3-phosphate acyltransferase activit y, not by increasing lysophosphatidic acid acyltransferase activity. F urthermore, the effects of L-FABP on phosphatidic acid biosynthesis co uld not be correlated with protection from acyl-CoA hydrolysis. L-FABP isoforms also influenced phospholipid fatty acid remodeling in a phos pholipid-dependent manner. Isoform I preferentially enhanced oleate an d palmitate esterification into phosphatidylethanol-amine, while isofo rm II stimulated esterification into phosphatidylcholine, phosphatidyl serine and sphingomyelin. Taken together, these data demonstrated a un ique role of each L-FABP isoform in modulating microsomally derived ph ospholipid fatty acid composition. (C) 1998 Elsevier Science B.V.