1-Acylglycerol-3-Phosphate O-Acyltransferase: An enzyme that catalyzes the acyl group transfer of ACYL COA to 1-acyl-sn-glycerol 3-phosphate to generate 1,2-diacyl-sn-glycerol 3-phosphate. This enzyme has alpha, beta, gamma, delta and epsilon subunits.Glycerol-3-Phosphate O-Acyltransferase: An enzyme that transfers acyl groups from acyl-CoA to glycerol-3-phosphate to form monoglyceride phosphates. It acts only with CoA derivatives of fatty acids of chain length above C-10. Also forms diglyceride phosphates. EC 220.127.116.11.Sterol O-Acyltransferase: An enzyme that catalyzes the formation of cholesterol esters by the direct transfer of the fatty acid group from a fatty acyl CoA derivative. This enzyme has been found in the adrenal gland, gonads, liver, intestinal mucosa, and aorta of many mammalian species. EC 18.104.22.168.Acyltransferases: Enzymes from the transferase class that catalyze the transfer of acyl groups from donor to acceptor, forming either esters or amides. (From Enzyme Nomenclature 1992) EC 2.3.1-Acylglycerophosphocholine O-Acyltransferase: An enzyme localized predominantly within the plasma membrane of lymphocytes. It catalyzes the transfer of long-chain fatty acids, preferentially unsaturated fatty acids, to lysophosphatides with the formation of 1,2-diacylglycero-3-phosphocholine and CoA. EC 22.214.171.124.Diacylglycerol O-Acyltransferase: An enzyme that catalyses the last step of the TRIACYLGLYCEROL synthesis reaction in which diacylglycerol is covalently joined to LONG-CHAIN ACYL COA to form triglyceride. It was formerly categorized as EC 126.96.36.199.Glycerolphosphate DehydrogenasePhosphates: Inorganic salts of phosphoric acid.Ghrelin: A 28-amino acid, acylated, orexigenic peptide that is a ligand for GROWTH HORMONE SECRETAGOGUE RECEPTORS. Ghrelin is widely expressed but primarily in the stomach in the adults. Ghrelin acts centrally to stimulate growth hormone secretion and food intake, and peripherally to regulate energy homeostasis. Its large precursor protein, known as appetite-regulating hormone or motilin-related peptide, contains ghrelin and obestatin.Glycerol-3-Phosphate Dehydrogenase (NAD+)Retinol O-Fatty-Acyltransferase: An enzyme that catalyzes the acyl group transfer of acyl COENZYME A to RETINOL to generate COENZYME A and a retinyl ester.Leucomycins: An antibiotic complex produced by Streptomyces kitasatoensis. The complex consists of a mixture of at least eight biologically active components, A1 and A3 to A9. Leucomycins have both antibacterial and antimycoplasmal activities.Acylation: The addition of an organic acid radical into a molecule.Receptors, Ghrelin: Transmembrane proteins that recognize and bind GHRELIN, a potent stimulator of GROWTH HORMONE secretion and food intake in mammals. Ghrelin receptors are found in the pituitary and HYPOTHALAMUS. They belong to the family of G-PROTEIN-COUPLED RECEPTORS.Glycerophospholipids: Derivatives of phosphatidic acid in which the hydrophobic regions are composed of two fatty acids and a polar alcohol is joined to the C-3 position of glycerol through a phosphodiester bond. They are named according to their polar head groups, such as phosphatidylcholine and phosphatidylethanolamine.AlbaniaGlycerophosphates: Any salt or ester of glycerophosphoric acid.
Glycerol-3-phosphate 2-O-acyltransferase: Glycerol-3-phosphate 2-O-acyltransferase (, sn-2-glycerol-3-phosphate O-acyltransferase, glycerol-3-phosphate O-acyltransferase) is an enzyme with system name acyl-CoA:sn-glycerol 3-phosphate 2-O-acyltransferase. This enzyme catalyses the following chemical reactionPhospholipid acyltransferase: A:146-305 A:146-305Glycerol phosphate shuttle: 380px|thumb|Glycerol Phosphate ShuttleSodium hexametaphosphateMacrocinAcylation: In chemistry, acylation (rarely, but more formally: alkanoylation) is the process of adding an acyl group to a compound. The compound providing the acyl group is called the acylating agent.Growth hormone secretagogue receptor: Growth hormone secretagogue receptor (GHSR), or ghrelin receptor, is a G protein-coupled receptor that binds ghrelin and plays a role in energy homeostasis and regulation of body weight. In the brain, they are located in the hypothalamic ventromedial nucleus and arcuate nucleus, as well as in ventral tegmental area dopamine neurons projecting to the nucleus accumbens.GlycerophospholipidBibliography of Albania: This is a list of books in the English language which deal with Albania and its geography, history, inhabitants, culture, biota, etc.
(1/250) Redundant systems of phosphatidic acid biosynthesis via acylation of glycerol-3-phosphate or dihydroxyacetone phosphate in the yeast Saccharomyces cerevisiae.
In the yeast Saccharomyces cerevisiae lipid particles harbor two acyltransferases, Gat1p and Slc1p, which catalyze subsequent steps of acylation required for the formation of phosphatidic acid. Both enzymes are also components of the endoplasmic reticulum, but this compartment contains additional acyltransferase(s) involved in the biosynthesis of phosphatidic acid (K. Athenstaedt and G. Daum, J. Bacteriol. 179:7611-7616, 1997). Using the gat1 mutant strain TTA1, we show here that Gat1p present in both subcellular fractions accepts glycerol-3-phosphate and dihydroxyacetone phosphate as a substrate. Similarly, the additional acyltransferase(s) present in the endoplasmic reticulum can acylate both precursors. In contrast, yeast mitochondria harbor an enzyme(s) that significantly prefers dihydroxyacetone phosphate as a substrate for acylation, suggesting that at least one additional independent acyltransferase is present in this organelle. Surprisingly, enzymatic activity of 1-acyldihydroxyacetone phosphate reductase, which is required for the conversion of 1-acyldihydroxyacetone phosphate to 1-acylglycerol-3-phosphate (lysophosphatidic acid), is detectable only in lipid particles and the endoplasmic reticulum and not in mitochondria. In vivo labeling of wild-type cells with [2-3H, U-14C]glycerol revealed that both glycerol-3-phosphate and dihydroxyacetone phosphate can be incorporated as a backbone of glycerolipids. In the gat1 mutant and the 1-acylglycerol-3-phosphate acyltransferase slc1 mutant, the dihydroxyacetone phosphate pathway of phosphatidic acid biosynthesis is slightly preferred as compared to the wild type. Thus, mutations of the major acyltransferases Gat1p and Slc1p lead to an increased contribution of mitochondrial acyltransferase(s) to glycerolipid synthesis due to their substrate preference for dihydroxyacetone phosphate. (+info)
(2/250) AMP-activated kinase reciprocally regulates triacylglycerol synthesis and fatty acid oxidation in liver and muscle: evidence that sn-glycerol-3-phosphate acyltransferase is a novel target.
AMP-activated kinase (AMPK) is activated in response to metabolic stresses that deplete cellular ATP, and in both liver and skeletal muscle, activated AMPK stimulates fatty acid oxidation. To determine whether AMPK might reciprocally regulate glycerolipid synthesis, we studied liver and skeletal-muscle lipid metabolism in the presence of 5-amino-4-imidazolecarboxamide (AICA) riboside, a cell-permeable compound whose phosphorylated metabolite activates AMPK. Adding AICA riboside to cultured rat hepatocytes for 3 h decreased [14C]oleate and [3H]glycerol incorporation into triacylglycerol (TAG) by 50% and 38% respectively, and decreased oleate labelling of diacylglycerol by 60%. In isolated mouse soleus, a highly oxidative muscle, incubation with AICA riboside for 90 min decreased [14C]oleate incorporation into TAG by 37% and increased 14CO2 production by 48%. When insulin was present, [14C]oleate oxidation was 49% lower and [14C]oleate incorporation into TAG was 62% higher than under basal conditions. AICA riboside blocked insulin's antioxidative and lipogenic effects, increasing fatty acid oxidation by 78% and decreasing labelled TAG 43%. Similar results on fatty acid oxidation and acylglycerol synthesis were observed in C2C12 myoblasts, and in differentiated C2C12 myotubes, AICA riboside also inhibited the hydrolysis of intracellular TAG. These data suggest that AICA riboside might inhibit sn-glycerol-3-phosphate acyltransferase (GPAT), which catalyses the committed step in the pathway of glycerolipid biosynthesis. Incubating rat hepatocytes with AICA riboside for both 15 and 30 min decreased mitochondrial GPAT activity 22-34% without affecting microsomal GPAT, diacylglycerol acyltransferase or acyl-CoA synthetase activities. Finally, purified recombinant AMPKalpha1 and AMPKalpha2 inhibited hepatic mitochondrial GPAT in a time-and ATP-dependent manner. These data show that AMPK reciprocally regulates acyl-CoA channelling towards beta-oxidation and away from glycerolipid biosynthesis, and provide strong evidence that AMPK phosphorylates and inhibits mitochondrial GPAT. (+info)
(3/250) A missense mutation accounts for the defect in the glycerol-3-phosphate acyltransferase expressed in the plsB26 mutant.
The sn-glycerol-3-phosphate acyltransferase (plsB) catalyzes the first step in membrane phospholipid formation. A conditional Escherichia coli mutant (plsB26) has a single missense mutation (G1045A) predicting the expression of an acyltransferase with an Ala349Thr substitution. The PlsB26 protein had a significantly reduced glycerol-3-phosphate acyltransferase specific activity coupled with an elevated Km for glycerol-3-phosphate. (+info)
(4/250) Rat sn-glycerol-3-phosphate acyltransferase: molecular cloning and characterization of the cDNA and expressed protein.
Rat mitochondrial glycerol-3-phosphate acyltransferase (GPAT) cDNA was cloned and characterized. We identified a cDNA containing an open reading frame of 828 amino acids that had an 89% homology with the coding region of the previously characterized mouse mitochondrial GPAT and a predicted amino acid sequence that was 96% identical. The rat 5' UTR was only 159 nucleotides, in contrast to the 926 nucleotide 5' UTR of the mouse cDNA and had an internal deletion of 167 nucleotides. GPAT was expressed in Sf21 insect cells, and specific inhibitors strongly suggest that, like the Escherichia coli GPAT, the recombinant mitochondrial GPAT and the mitochondrial GPAT isoform in rat liver contain critical serine, histidine, and arginine residues. (+info)
(5/250) Phosphatidic acid synthesis in mitochondria. Topography of formation and transmembrane migration.
The topography of formation and migration of phosphatidic acid (PA) in the transverse plane of rat liver mitochondrial outer membrane (MOM) were investigated. Isolated mitochondria and microsomes, incubated with sn-glycerol 3-phosphate and an immobilized substrate palmitoyl-CoA-agarose, synthesized both lyso-PA and PA. The mitochondrial and microsomal acylation of glycerophosphate with palmitoyl-CoA-agarose was 80-100% of the values obtained in the presence of free palmitoyl-CoA. In another series of experiments, both free polymyxin B and polymyxin B-agarose stimulated mitochondrial glycerophosphate acyltransferase activity approximately 2-fold. When PA loaded mitochondria were treated with liver fatty acid binding protein, a fifth of the phospholipid left the mitochondria. The amount of exportable PA reduced with the increase in the time of incubation. In another approach, PA-loaded mitochondria were treated with phospholipase A(2). The amount of phospholipase A(2)-sensitive PA reduced when the incubation time was increased. Taken together, the results suggest that lysophosphatidic acid (LPA) and PA are synthesized on the outer surface of the MOM and that PA moves to the inner membrane presumably for cardiolipin formation. (+info)
(6/250) A conserved seven amino acid stretch important for murine mitochondrial glycerol-3-phosphate acyltransferase activity. Significance of arginine 318 in catalysis.
Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the initial and committed step in glycerolipid biosynthesis. We previously cloned the cDNA sequence to murine mitochondrial GPAT (Yet, S-F., Lee, S., Hahm, Y. T., and Sul, H.S. (1993) Biochemistry 32, 9486-9491). We expressed the protein in insect cells which was targeted to mitochondria, purified, and reconstituted mitochondrial GPAT activity using phospholipids (Yet, S.-F., Moon, Y., and Sul, H. S. (1995) Biochemistry 34, 7303-7310). Deletion of the seven amino acids from mitochondrial GPAT, (312)IFLEGTR(318), which is highly conserved among acyltransferases in glycerolipid biosynthesis, drastically reduced mitochondrial GPAT activity. Treatment of mitochondrial GPAT with arginine-modifying agents, phenylglyoxal and cyclohexanedione, inactivated the enzyme. Two highly conserved arginine residues, Arg-318, in the seven amino stretch, and Arg-278, were identified. Substitution of Arg-318 with either alanine, histidine, or lysine reduced the mitochondrial GPAT activity by over 90%. On the other hand, although substitution of Arg-278 with alanine and histidine decreased mitochondrial GPAT activity by 90%, replacement with lysine reduced activity by only 25%. A substitution of the nonconserved Arg-279 with either alanine, histidine, or lysine did not alter mitochondrial GPAT activity. Moreover, R278K mitochondrial GPAT still showed sensitivity to arginine-modifying agents, as in the case of wild-type mitochondrial GPAT. These results suggest that Arg-318 may be critical for mitochondrial GPAT activity, whereas Arg-278 can be replaced by a basic amino acid. Examination of the other conserved residues in the seven amino acid stretch revealed that Phe-313 and Glu-315 are also important, but conservative substitutions can partially maintain activity; substitution with alanine reduced activity by 83 and 72%, respectively, whereas substituting Phe-313 with tyrosine and Glu-315 with glutamine had even lesser effect. In addition, there was no change in fatty acyl-CoA selectivity. Kinetic analysis of the R318K and R318A mitochondrial GPAT showed an 89 and 95%, respectively, decrease in catalytic efficiency but no major change in substrate binding as indicated by the K(m) values for palmitoyl-CoA and glycerol 3-phosphate. These studies indicate importance of the conserved seven amino acid stretch for mitochondrial GPAT activity and the significance of Arg-318 for catalysis. (+info)
(7/250) Microsomal fatty acyl-CoA transacylation and hydrolysis: fatty acyl-CoA species dependent modulation by liver fatty acyl-CoA binding proteins.
arachidonoyl-CoA. In summary, the data established for the first time a role for both L-FABP and ACBP in microsomal phosphatidic acid biosynthesis. By preferentially stimulating microsomal transacylation of unsaturated long chain fatty acyl-CoAs while concomitantly exerting their differential protection from microsomal acyl-CoA hydrolase, L-FABP and ACBP can uniquely function in modulating the pattern of fatty acids esterified to phosphatidic acid, the de novo precursor of phospholipids and triacylglycerols. This may explain in part the simultaneous presence of these proteins in cell types involved in fatty acid absorption and lipoprotein secretion. (+info)
(8/250) Regulation of the fatty acid synthase promoter by insulin.
Expression of critical enzymes in fatty acid and fat biosynthesis is tightly controlled by nutritional and hormonal stimuli. The expression of fatty acid synthase, which catalyzes all reactions for synthesis of palmitate from acetyl-CoA and malonyl-CoA, and of mitochondrial glycerol-3-phosphate acyltransferase, which catalyzes the first acylation step in glycerophospholipid synthesis, is decreased to an undetectable level during fasting. Food intake, especially a high carbohydrate, fat-free diet after fasting, causes a dramatic increase in the transcription of these genes. Insulin secretion is increased during feeding and has a positive effect on expression. By using adipocytes in culture and transgenic mice that express the reporter gene driven by the fatty acid synthase promoter, the cis-acting sequence that mediates insulin regulation of the fatty acid synthase promoter was defined. Upstream stimulatory factors (USF) that bind to the -65 E-box are required for insulin-mediated transcriptional activation of the fatty acid symthase gene. Sterol regulatory element binding protein (SREBP)-1 may be also involved in induction of these genes during feeding. Using specific inhibitors and expressing various signaling molecules, we found that insulin regulation of the fatty acid synthase promoter is mediated by the phosphatidylinositol (PI)3-kinase signaling pathway and that protein kinase B/akt is a downstream effector. (+info)
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