IngentaConnect Fatty Acid Binding Protein: Stimulation of Microsomal Phosphatidi...

Authors: Jolly C.A.¹; Hubbell T.¹; Behnke W.D.²; Schroeder F.¹

Source: Archives of Biochemistry and Biophysics, Volume 341, Number 1, May 1997 , pp. 112-121(10)

Abstract:

The effect of fatty acid binding proteins (FABPs) on two key steps of microsomal phosphatidic acid formation was examined. Rat liver microsomes were purified by size-exclusion chromatography to remove endogenous cytosolic fatty acid and fatty acyl-CoA binding proteins while recombinant FABPs were used to avoid cross-contamination with such proteins from native tissue. Neither rat liver (L-FABP) nor rat intestinal fatty acid binding protein (I-FABP) stimulated liver microsomal fatty acyl-CoA synthase. In contrast, L-FABP and I-FABP enhanced microsomal conversion of [ 14 C]oleoyl-CoA and glycerol 3-phosphate to [ 14 C]phosphatidic acid by 18- and 7-fold, respectively. The mechanism for this stimulation, especially by I-FABP, is not known. However, several observations presented here suggest that, like L-FABP, I-FABP may interact with fatty acyl-CoA and thereby stimulate enzyme activity. First, I-FABP decreased microsomal membrane-bound oleoyl-CoA. Second, oleoyl-CoA displaced I-FABP bound fluorescent fatty acid, cis -parinaric acid, with K i of 5.3 mu m and 1.1 sites. Third, oleoyl-CoA decreased I-FABP tryptophan fluorescence with a K d of 4.2 mu m . Fourth, oleoyl-CoA red shifted emission spectra of acrylodated I-FABP, a sensitive marker of I-FABP interactions with ligands. In summary, the results demonstrate for the first time that both L-FABP and I-FABP stimulate liver microsomal phosphatidic acid formation by enhancing synthesis of phosphatidate from fatty acyl-CoA and glycerol 3-phosphate.

Keywords: fatty acid binding protein; phosphatidic acid; microsomes; liver; intestine; fatty acyl-CoA

Language: English

Document Type: Research article

Affiliations: 1: Department of Physiology and Pharmacology, Texas A & M University, TVMC, College Station, Texas, 77843-4466 2: Department of Molecular Genetics, University of Cincinnati Medical Center, M.L. 0524, Cincinnati, Ohio, 45267-0524

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Fatty Acid Binding Protein: Stimulation of Microsomal Phosphatidic Acid Formation