Fatty acid binding protein: stimulation of microsomal phosphatidic acid formation.
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.
Jolly
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CA
Department of Physiology and Pharmacology, Texas A & M University 77843-4466, USA.
Hubbell
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T
Behnke
W D
WD
Schroeder
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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
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