title: Fatty acid binding protein: stimulation of microsomal phosphatidic acid formation.
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 [14C]oleoyl-CoA and glycerol 3-phosphate to [14C]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 Ki of 5.3 microM and 1.1 sites. Third, oleoyl-CoA decreased I-FABP tryptophan fluorescence with a Kd of 4.2 microM. 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.
authors.affiliation: Department of Physiology and Pharmacology, Texas A & M University 77843-4466, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Jolly
authors.forename: T
authors.initials: T
authors.lastname: Hubbell
authors.forename: W D
authors.initials: WD
authors.lastname: Behnke
authors.forename: F
authors.initials: F
authors.lastname: Schroeder
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D003066:Coenzyme A Ligases / Q000378:metabolism; D026261:Diazepam Binding Inhibitor; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005456:Fluorescent Dyes; D005994:Glycerophosphates / Q000378:metabolism; D007422:Intestines / Q000737:chemistry; D008099:Liver / Q000737:chemistry; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D018996:Myelin P2 Protein / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D013050:Spectrometry, Fluorescence; D014364:Tryptophan; D015854:Up-Regulation / Q000502:physiology; D000098859:Long-Chain-Fatty-Acid-CoA Ligase
chemical_list: D000214:Acyl Coenzyme A; D002352:Carrier Proteins; D026261:Diazepam Binding Inhibitor; C493320:Fabp1 protein, mouse; C493321:Fabp1 protein, rat; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D005456:Fluorescent Dyes; D005994:Glycerophosphates; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010712:Phosphatidic Acids; D011994:Recombinant Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C017585:oleoyl-coenzyme A; D019301:Oleic Acid; D014364:Tryptophan; C029620:alpha-glycerophosphoric acid; D003066:Coenzyme A Ligases; C090799:FAA2 protein, S cerevisiae; D000098859:Long-Chain-Fatty-Acid-CoA Ligase; C013641:parinaric acid