SEARCH · PubMed Health

Results for “ACYLTRANSFERASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

PubMed1984

Comparison of 1-acylglycerophosphate and glycerophosphate acyltransferases from Euglena microsomes.

Both glycerophosphate and monoacylglycerophosphate acyltransferases from Euglena microsomes were inhibited by N-ethylmaleimide, but their responses to heat inactivation and sn-glyceraldehyde-3-phosphate differed. Glycerophosphate acyltransferase had a higher V with palmitoyl-CoA compared to oleoyl-CoA; the reverse was true for monoacylglycerophosphate acyltransferase. Km's (microM) for the glycerophosphate acyltransferase were: palmitoyl-CoA, 21; oleoyl-CoA, 14; and sn-glycerol-3-phosphate, 2900. Km's (microM) for monoacylglycerophosphate acyltransferase were: palmitoyl-CoA, 7; oleoyl-CoA, 4; and 1-palmitoyl-sn-glycerol-3-phosphate, 48.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗

PubMed1993

Developmental Profile of Diacylglycerol Acyltransferase in Maturing Seeds of Oilseed Rape and Safflower and Microspore-Derived Cultures of Oilseed Rape.

Diacylglycerol acyltransferase (EC 2.3.1.20) activity was assayed during the maturation of seeds of oilseed rape (Brassica napus L.) and safflower (Carthamus tinctorius L.). Developmental studies were also conducted with microspore-derived embryos of oilseed rape (B. napus L. cv Topas) and an embryogenic microspore-derived cell-suspension culture of winter oilseed rape (B. napus L. cv Jet Neuf). In the maturing seeds, diacylglycerol acyltransferase activity increased to a maximum during rapid accumulation of lipid and declined, thereafter, with seed maturity. In microspore-derived embryos of oilseed rape (cv Topas), high levels of diacylglycerol acyltransferase activity were found throughout the early torpedo to late cotyledonary developmental stages with maximum enzyme specific activity associated with the mid-cotyledonary developmental stage. The cell-suspension culture of winter oilseed rape (cv Jet Neuf) contained 3 to 4% triacylglycerol on a dry weight basis and represented about half of the total lipid. The fatty acid profile of total lipid and triacylglycerol in the cell-suspension culture was similar in samples taken during a 1-year period. The Jet Neuf culture contained diacylglycerol acyltransferase with specific activity similar to that of Topas microspore-derived embryos. Jet Neuf diacylglycerol acyltransferase also displayed an enhanced specificity for erucoyl-CoA over oleoyl-CoA when assayed with 14 [mu]M acyl-coenzyme A in the reaction mixture. The specific activity of diacylglycerol acyltransferase in homogenates prepared from the Jet Neuf culture ranged from 5 to 15 pmol of triacylglycerol min-1 mg-1 of protein when assayed at intervals during a period of 1 year. Thus, the cell-suspension culture may represent an attractive tissue source for purification and characterization of triacyl-glycerol biosynthetic enzymes.

Journal Article↗

PubMed1975

The acyltransferase activity of adrenal medulla and sacroplasmic reticulum of skeletal muscles.

The presence of acyl-CoA-lysolecithin-acyltransferase was studied in ox adrenal medulla fractionated by sucrose gradient centrifugation. The highest activity of this enzyme is localized in the microsomes and not in the membranes of chromaffin granules. Estimation of acyltransferase activity in fragments of sarcoplasmic reticulum (SR) from rabbit skeletal muscles before and after sucrose gradient centrifugation shows that in these membranes acyltransferase is a membrane bound enzyme. Both enzyme preparations transfer 18-carbon fatty acids in increasing order of unsaturation to 1-acyl-sn-glycer-3-phosphorylcholine (1-acyl-GPC) (18:0 less than 18:1 less than 18:2) and in decreasing order to 2-acyl-sn-glycero-3-phosphorylcholine (2-acyl-GPC) (18:0 greater than 18:1 greater than 18:2). For the acyltransferase present in ox adrenal medulla and fragments of sarcoplasmic reticulum, 1-acyl-sn-glycero-3-phosphorylethanolamine (1-acyl-GPE) is not a good acyl acceptor. The importance of acyltransferase in the de- and re-acylation cycle for the neogenesis of membranes-specific lecithin is discussed.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1990

The medium-chain carnitine acyltransferase activity associated with rat liver microsomes is malonyl-CoA sensitive.

The data presented herein show that both rough and smooth endoplasmic reticulum contain a medium-chain/long-chain carnitine acyltransferase, designated as COT, that is strongly inhibited by malonyl-CoA. The average percentage inhibition by 17 microM malonyl-CoA for 25 preparations is 87.4 +/- 11.7, with nine preparations showing 100% inhibition; the concentrations of decanoyl-CoA and L-carnitine were 17 microM and 1.7 mM, respectively. The concentration of malonyl-CoA required for 50% inhibition is 5.3 microM. The microsomal medium-chain/long-chain carnitine acyltransferase is also strongly inhibited by etomoxiryl-CoA, with 0.6 microM etomoxiryl-CoA producing 50% inhibition. Although palmitoyl-CoA is a substrate at low concentrations, the enzyme is strongly inhibited by high concentrations of palmitoyl-CoA; 50% inhibition is produced by 11 microM palmitoyl-CoA. The microsomal medium-chain/long-chain carnitine acyltransferase is stable to freezing at -70 degrees C, but it is labile in Triton X-100 and octylglucoside. The inhibition by palmitoyl-CoA and the approximate 200-fold higher I50 for etomoxiryl-CoA clearly distinguish this enzyme from the outer form of mitochondrial carnitine palmitoyltransferase. The microsomal medium-chain/long-chain carnitine acyltransferase is not inhibited by antibody prepared against mitochondrial carnitine palmitoyltransferase, and it is only slightly inhibited by antibody prepared against peroxisomal carnitine octanoyltransferase. When purified peroxisomal enzyme is mixed with equal amounts of microsomal activity and the mixture is incubated with the antibody prepared against the peroxisomal enzyme, the amount of carnitine octanoyltransferase precipitated is equal to all of the peroxisomal carnitine octanoyltransferase plus a small amount of the microsomal activity. This demonstrates that the microsomal enzyme is antigenically different than either of the other liver carnitine acyltransferases that show medium-chain/long-chain transferase activity. These results indicate that medium-chain and long-chain acyl-CoA conversion to acylcarnitines by microsomes in the cytosolic compartment is also modulated by malonyl-CoA.

Acyl Coenzyme A↗

PubMed1980

On the mechanism of regulation of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase and of acyl coenzyme A:cholesterol acyltransferase by dietary fat.

The activity and the kinetic properties of hydroxymethylglutaryl-CoA reductase and of acyl-CoA:cholesterol acyltransferase in the liver microsomal fraction have been compared between rats fed on either unsaturated or on saturated fat. When rats wre fed for 12h on a compounded diet containing either safflower seed oil or tristearin the composition of the fatty acyl chains of the microsomal phospholipids was shown to be relatively more unsaturated in the rats that received the unsaturated fat. The activity of hydroxymethylglutaryl-CoA reductase in the microsomal fraction was considerably reduced in rats fed on compounded diet containing unsaturated fat whereas this dietary condition resulted in a considerable increase in the activity of acyl-CoA:cholesterol acyltransferase. Similar effects were observed after feeding rats for 12 h on a commercial diet supplemented with either safflower seed oil or with tristearin. The addition of 2% cholesterol to the fat-supplemented diets resulted in both cases in a decrease in hydroxymethylglutaryl-CoA reductase and an increse in acyl-CoA:cholesterol acyltransferase activity as compared with the corresponding values from the rats fed on the fat-supplemented diets with no cholesterol. The Arrhenius plots of hydroxymethylgutaryl-CoA reductase in the microsomal fraction from rats fed on fat-supplemented commercial diet for 12 h showed breaks in the activation energy at 29.6 degrees C for the preparations from rats fed on tristearin and 28 degrees C for those from rats fed on safflower seed oil. The activation energy of the enzyme was lower above and higher below the break for the preparations from rat fed on the unsaturated fat-supplemented diet. Similar differences were obtained from the comparison of the Arrhenius plots in the preparations from rats fed on saturated fat and those in the preparations from rats fed on unsaturated fat when the diet was compounded and given to the animals for 36 h. The addition of 2% cholesterol to the commercial diet supplemented with either saturated or unsaturated fat resulted in Arrhenius plots with a constant activation energy between 37 and 22 degrees C for the enzyme in microsomal preparations from both groups of rats. The apparent Km value for hydroxymethylglutaryl-CoA was lower for the reductase in microsomal preparations from rats fed on the unsaturated fat as compared with that for the enzyme in microsomal preparations from rats fed on saturated fat. There was also a decrease in the apparent Km value for oleic acid for the acyltransferase from rats fed on unsaturated fat as compared with that for the enzyme in the microsomal preparation from the rats fed on saturated fat. The results of the present study are consistent with higher concentration of free cholesterol in endoplasmic reticular membrane in the environment of the reductase and that of acyltransferase following the administration of dietary unsaturated fat as compared with that following the administation of saturated fat.

Acyltransferases↗

PubMed1981

Modulation of diacylglycerol acyltransferase by lysophosphatidylcholine and related monochain phospholipids.

Acyl-CoA : 1,2-diacylglycerol O-acyltransferase (EC 2.3.1.20) activity of rat liver microsomes was found to be stimulated by 1-acyl-sn-glycero-3-phosphocholine at low concentrations, but was inhibited above 0.2 mM. Diacylglycerol acylation was optimal at 75 microM lysophosphatidylcholine, resulting in a more than 2-fold activation of the enzyme. Acyltransferase activity disappeared above 0.5 mM lysophosphatidylcholine levels. 0.05% sodium taurocholate supplementation reduced diacylglycerol acyltransferase activity by approx. 2/3 over the entire range of lysophosphatidylcholine concentrations. 1-O-Hexadecylpropanediol-3-phosphocholine was shown to mimic lysophosphatidylcholine at stimulatory and at inhibitory concentrations in the absence and in the presence of sodium taurocholate, thus ruling out acyl-CoA depletion due to lysophosphatidylcholine acylation as a cause of depressed triacylglycerol synthesis at higher lysophosphatidylcholine levels. 1-Acyl-sn-glycero-3-phosphoethanolamine stimulated diacylglycerol acyltransferase to a lesser extent, without showing inhibition at higher concentrations. The data point towards a direct effect of the lysophospholipids on the acyltransferase system.

Acyltransferases↗

PubMed1982

Localization of glycerophosphate acyltransferase in Escherichia coli.

sn-Glycero-3-phosphate acyltransferase (EC 2.3.1.15) the first enzyme involved in phospholipid biosynthesis, is known to be associated with the cytoplasmic membrane of Escherichia coli. The localization of this enzyme in the transverse plane of the membrane was investigated by proteolysis of intact and lysed spheroplasts and by inhibition of glycerol 3-phosphate transport into intact cells in the presence of azide. Glycerophosphate acyltransferase was found to be resistant to proteolysis by trypsin in intact spheroplasts, whereas its enzymatic activity could be destroyed completely by trypsin in lysed spheroplasts. These results are in line with a localization of the acyltransferase at the inner aspect of the cytoplasmic membrane. Sodium azide was shown to have no inhibitory effect on glycerophosphate acyltransferase activity. Lack of incorporation of glycero phosphate into the phospholipids of glycerol phosphate transport-negative cells and inhibition of this incorporation in wild-type and glycerol 3-phosphate transport-constitutive cells by azide support a cytoplasmic-oriented localization of the glycerophosphate acyltransferase.

Acyltransferases↗

PubMed1983

Activity of acyl-CoA: cholesterol acyltransferase and 3-hydroxy-3-methylglutaryl-CoA reductase in subfractions of hepatic microsomes enriched with cholesterol.

The influence of membrane cholesterol on the activities of acyl-CoA: cholesterol acyltransferase and 3-hydroxy-3-methylglutaryl-CoA reductase was examined in three microsomal subfractions (RNA-rich, RNA-poor, and smooth) that had been enriched with cholesterol by incubation with mixed lipoproteins from hypercholesterolemic rabbit serum. Acyl-CoA: cholesterol acyltransferase activity was significantly stimulated in the three subfractions, particularly in the RNA-rich microsomal component. 3-Hydroxy-3-methylglutaryl-CoA reductase, on the other hand, was suppressed (30%) in only one (RNA-poor) of the three microsomal subfractions, despite a 1.4-fold increase in the concentration of membrane cholesterol. An attempt was made to distinguish between an effect based exclusively on an increase in available cholesterol substrate and an activation of acyl-CoA: cholesterol acyltransferase in RNA-rich microsomes enriched with cholesterol. An experimental design was devised so that substrate cholesterol was provided in the form of heated smooth microsomes and acyl-CoA: cholesterol acyltransferase was provided as a separate preparation in the form of RNA-rich microsomes. Appropriate controls were carried out to test for transfer of cholesteryl ester between the two sets of particles. The results suggested that cholesterol enhanced acyl-CoA: cholesterol acyltransferase activity by serving both as a substrate and as a non-substrate modulator.

Acyltransferases↗

PubMed1988

Hepatic sn-glycerol-3-phosphate acyltransferases: effect of monoacylglycerol analogs on mitochondrial and microsomal activities.

The regulation of cellular diacylglycerol levels may have important consequences for protein kinase C activity. Because monoacylglycerols were said to inhibit the committed step of glycerolipid synthesis, the sn-glycerol-3-P acyltransferase (glycerol-P acyltransferase), we determined (1) whether both the mitochondrial and the microsomal glycerol-P acyltransferase isoenzymes were inhibited by 1- and 2-mono-18:1-glycerols, and their ether and amide analogs and (2) what the mechanism of inhibition was. 1- and 2-mono-18:1-glycerols, their ether and amide analogs, and 1-mono-18:1-glycerol 3-phosphate were all competitive inhibitors of the microsomal glycerol-P acyltransferase activity. The relative Ki values suggested that inhibition was strongest with the radyl group at the sn-1 position and that an oxygen bond is important at the sn-1 position. Although the monoacyl- and monoalkylglycerols were also competitive inhibitors of the mitochondrial glycerol-P acyltransferase, neither of the amide analogs was an inhibitor, suggesting that an oxygen bond is essential at both the sn-1 and sn-2 positions. Because monoradylglycerols inhibit several enzyme activities that contribute to the biosynthesis or the metabolism of diacylglycerol, these inhibitors may function within cells in part to regulate cellular diacylglycerol levels.

Acyltransferases↗

PubMed1990

Changes in the activities of dihydroxyacetone phosphate and glycerol-3-phosphate acyltransferases in rat liver under various conditions.

Activities of enzymes relating to the acyl dihydroxyacetone phosphate (acyl DHAP) pathway were determined in rat liver under conditions known to elevate the peroxisomal beta-oxidation activity. In fasted and streptozotocin-induced diabetic rats, DHAP acyltransferase activity showed a small but significant increase, though the activities of glycerol-3-phosphate (GP) acyltransferase and alkyl DHAP synthase were not changed. After 2 weeks, feeding of 20% partially hydrogenated marine oil, the activity of DHAP acyltransferase also increased to 140% of the control. The feeding of 0.25% clofibrate and 2% di(2-ethylhexyl)phthalate (DEHP) increased the activities of both DHAP and GP acyltransferases by 2- to 3-fold, whereas alkyl DHAP synthase activity decreased under the same conditions. A fractionation study showed that the increases in the activities of DHAP acyltransferase and acyl/alkyl DHAP reductase in the liver of rats treated with DEHP occurred mainly in peroxisomes and microsomes, respectively. The phospholipid contents per mg protein of the isolated hepatic peroxisomes from rats were as follows (percent of the control): fasting, 62%; diabetic, 69%; high fat-diet, 89%; clofibrate-treated, 126%; DEHP-treated, 119%. These results suggest that glycerophospholipid metabolism might also be controlled by peroxisomal enzymes under physiological and pathological conditions.

Acyltransferases↗

PubMed1993

Lysosomal phosphatidylcholine: bis(monoacylglycero)phosphate acyltransferase: specificity for the sn-1 fatty acid of the donor and co-purification with phospholipase A1.

Positional specificities in donor and acceptor phospholipids of the lysosomal phosphatidylcholine: bis(monoacylglycero)phosphate acyltransferase have been determined. Comparison of the transfer of labelled fatty acid from sn-1 [14C]acyl and sn-2 [14C]acylphosphatidylcholines by extracts of rat liver lysosomes revealed that fatty acids in the sn-1 position were exclusively transferred. Degradation of the acylphosphatidylglycerol product by Rhizopus arrhizus lipase, highly specific for fatty acids esterified to sn-1 or sn-3 positions, indicated that sn-1 or sn-3 rather than sn-2 positions had been acylated. Assays of phospholipase A1, phosphatidylcholine: bis(monoacylglycero)phosphate acyltransferase, the conversion of lysophosphatidylglycerol to bis(monoacylglycero)phosphate and phospholipase A2 were performed at various steps in the purification of lysosomal phospholipase A1. After the penultimate step of chromatofocusing, there was a 1086-fold increase of phospholipase A1 specific activity over the homogenate and this was accompanied by a 11 998-fold increase of phosphatidylcholine: bis(monoacylglycero)phosphate acyltransferase specific activity. A second preparation carried through to the final step of gel-filtration retained a similar ratio of acyltransferase activity. On the other hand, specific activities of phospholipase A2 and of the conversion of lysophosphatidylglycerol to bis(monoacylglycero)phosphate increased to the step where enzyme was solubilized from lysosomes, but were lost from later steps. These findings suggest that phosphatidylcholine: bis(monoacylglycero)phosphate acyltransferase is catalyzed by lysosomal phospholipase A1. The site of acylation in the bis(monoacylglycero)phosphate acceptor appears to be either sn-1 or sn-3. Since the lysosomal extracts did not catalyze the transacylation of phosphatidylglycerol, we conclude that the formation of acylphosphatidylglycerol in lysosomes requires the sequential acylation of lysophosphatidylglycerol to form bis(monoacylglycero)phosphate by an unidentified enzymatic mechanism followed by a transacylation of bis(monoacylglycero)phosphate in either sn-1 or sn-3 position to form acylphosphatidylglycerol which is catalyzed by phospholipase A1.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗

PubMed1980

Inhibition of acyltransferase in lymphocytes by concanavalin A.

The effects of concanavalin A and succinylated concanavalin A on the transformation of mouse splenic lymphocytes, and on early biochemical events in the transformation, were compared. 1. The transformation of lymphocytes is biphasic with respect to concanavalin A concentration with optimal activation at about 1 microgram/ml. Activation by succinyl concanavalin A is not biphasic over a range of lectin concentration of 1--16 microgram/ml. 2. In intact lymphocytes cultured for 4 h, the enzyme Acyl-CoA:1-acylglycero-3-phosphocholine O-acyltransferase (EC 2.3.1.23) was not activated by concanavalin A but was inhibited at all concentrations tested, and was about 60% inhibited at 16 micrograms concanavalin A per ml. Succinyl concanavalin A gave little or no inhibition at similar concentrations. 3. Lymphocytes become committed to divide while their acyltransferase activities are markedly inhibited by concanavalin A. 4. The inhibition of acyltransferase by concanavalin A can be lifted by displacing the lectin from the cells by alpha-methylmannoside. Lowered enzyme activity is not caused by cell agglutination or by direct cross-linking of lectin receptors. It is unlikely that the inhibition of acyltransferase is due to indirect cross-linking via the cytoskeleton since colchicine did not reverse the inhibition. 5. The inhibition of acyltransferase and the reduced stimulation of transformation by higher levels of concanavalin A appear to be due to hydrophobic interaction of the lectin with the plasma membrane, as shown by liposome aggregation studies.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1984

Development of glycerophosphate acyltransferase in guinea pig lung mitochondria and microsomes.

Development of mitochondrial and microsomal glycerophosphate acyltransferase in the fetal guinea pig lung was investigated. Mitochondrial and microsomal enzyme activity gradually increased from 45 days to 55 days of gestation. The specific activity in the microsomal fraction (8.2 nmol/min per mg protein) then declined until term, but increased again in the 24-h newborn from 2.5 to 6.1 nmol/min per mg protein. Glycerophosphate acyltransferase activity in the mitochondrial fraction declined after 55 days (3.5 nmol/min per mg) to a minimum level at 60 days (1.8 nmol/min per mg), but increased again in the 24-h newborn (4.0 nmol/min per mg). The specific activity of both mitochondrial and microsomal enzyme declined after 24 h after birth until adult levels were attained. Glycerophosphate acyltransferase activity in mitochondria and microsomes from adult lung was 0.8 and 2.0 nmol/min per mg, respectively. Microsomal enzyme activity was consistently inhibited (over 95%) throughout gestation and adulthood by exposure to any one of several proteinases: trypsin, chymotrypsin, papain, bromelain, pronase and nagarse. Although mitochondrial enzyme activity was also inhibited by these proteinases, there was a continuous increase in proteinase-resistant glycerophosphate acyltransferase activity between 45 days of gestation and term. In contrast, adult mitochondrial enzyme activity was stimulated by all the proteinases studied. These results suggest that early in gestation, glycerophosphate acyltransferase lies more exposed on the cytoplasmic side of the mitochondrial outer membrane and as gestation progresses it becomes embedded into the phospholipid bilayer.

Acyltransferases↗

PubMed2003

Stability of diacylglycerol acyltransferase in dehydrated bovine muscle tissue.

Meaningful estimates of diacylglycerol acyltransferase (EC 2.3.1.20) activity in different tissue samples require effective, unbiased methods of sample storage. Samples of the pars costalis diaphragmatis muscle (skirt muscle of the diaphragm) were obtained from 18- to 20-month-old cattle and assayed for microsomal protein content and diacylglycerol acyltransferase activity after having been stored under various conditions as dissected tissue or microsomes prepared from dissected tissue. There was relative enrichment of diacylglycerol acyltransferase specific activity (p<0.05) when samples prepared from the pars costalis diaphragmatis muscle were dehydrated and stored for 2 weeks, as compared to the control condition (in which the microsome fraction was prepared from fresh pars costalis diaphragmatis muscle and assayed immediately). The results suggested that dehydration was an effective method of storage for bovine muscle samples destined for estimation of the microsomal diacylglycerol acyltransferase activity. The dehydration approach for preparing samples for analysis of diacylglycerol acyltransferase activity might also prove useful to investigators who are interested in obtaining reliable estimates of the activity of other enzymes in tissue samples.

Acyltransferases↗

PubMed1983

Membrane lipid metabolism in Chlamydomonas reinhardtii 137+ and y-1: II. Cytochemical localization of acyltransferase activities.

We have cytochemically localized the acyltransferase activities in the alga Chlamydomonas reinhardtii. Glycerol 3-phosphate (G3P) acyltransferase and lysophosphatidate (LPA) acyltransferase activities were cytochemically assayed utilizing biochemically optimized reaction conditions (Jelsema et al., 1982). The cytochemical assays clearly demonstrate that in the wild-type cells (137+) and the y-1 mutant, both enzymes were present in the photosynthetic membranes, envelope, and pyrenoid tubules of the chloroplast. Activity was also localized to the Golgi apparatus and its associated vesicles. Additionally, LPA acyltransferase activity was found associated with the outer mitochondrial membranes. The cytochemical data from this study confirm the biochemical data obtained using purified chloroplast membranes (Jelsema et al., 1982) and establishes the presence of these glycerolipid-synthesizing enzymes in the photosynthetic membranes of the chloroplast. These findings support the earlier reports of the presence and activity of lipid-synthesizing enzymes in the chloroplast, and also is in agreement with the postulated role of the pyrenoid tubules in the synthesis of the thylakoid membranes. This report differs in that these lipid-synthesizing enzymes have been localized to the chloroplast photosynthetic membranes themselves as well as exhibiting significant levels of activity for both enzymes in the Golgi apparatus. During light-induced chloroplast biogenesis in the yellow mutant of C. reinhardtii (y-1), the photosynthetic membranes appear to be the primary site of acyltransferase activity, suggesting that in situ synthesis of the membrane lipids during this period of rapid membrane formation is the primary mode for the synthesis of the thylakoid lipids. That these intrinsic thylakoid enzyme activities are not exclusively a function of the growth phase of the cell, but are found in mature chloroplast of the 137+ cells as well, further supports the conclusion that the photosynthetic membranes of the chloroplast have the capacity for synthesis of their own membrane lipids.

Acyltransferases↗

PubMed1983

A trypsin-sensitive, heat-labile, N-ethylmaleimide-sensitive factor in adipocyte post-microsomal supernatant which affects the assay of adipocyte glycerol phosphate acyltransferase activities.

Addition of adipocyte 100 000 g post-microsomal supernatant to assays of glycerol phosphate acyltransferase in isolated mitochondria or microsomal fractions decreased activity at lower concentrations of palmitoyl-CoA. At higher concentrations of palmitoyl-CoA, activation was observed on addition of post-microsomal supernatant. The effect of post-microsomal supernatant to decrease activity at lower [palmitoyl-CoA] was abolished by heating or by trypsin treatment, and was also abolished by addition of N-ethylmaleimide to assays or by pretreatment of post-microsomal supernatant with N-ethylmaleimide. The stimulatory effect seen at higher [palmitoyl-CoA] was not sensitive to heat or trypsin treatment. The effect of post-microsomal supernatant at lower [palmitoyl-CoA] cannot be attributed to palmitoyl-CoA hydrolase activity. It was found that brief treatment of adipocyte mitochondria with low concentrations of trypsin was an effective way to remove contaminating microsomal glycerol phosphate acyltransferase activity. Adipocyte post-microsomal supernatant was more effective than an equivalent quantity of liver post-microsomal supernatant protein in decreasing adipocyte microsomal glycerol phosphate acyltransferase activity. The effects of the supernatants from both tissues were decreased by flavaspidic acid. Semi-purified Z-protein fraction from rat liver did not mimic the effect of adipocyte post-microsomal supernatant to decrease glycerol phosphate acyltransferase at lower [palmitoyl-CoA]. Post-microsomal supernatants obtained from noradrenaline-treated adipocytes were less effective than those from control cells in decreasing glycerol phosphate acyltransferase activity in microsomal fractions at lower [palmitoyl-CoA]. It is suggested that adipocyte cytosol may contain an acyl-CoA-binding protein or proteins differing from Z-protein in some respects. The physiological significance of the findings is briefly discussed.

Acyltransferases↗

PubMed2002

A novel bifunctional wax ester synthase/acyl-CoA:diacylglycerol acyltransferase mediates wax ester and triacylglycerol biosynthesis in Acinetobacter calcoaceticus ADP1.

Triacylglycerols (TAGs) and wax esters are neutral lipids with considerable importance for dietetic, technical, cosmetic, and pharmaceutical applications. Acinetobacter calcoaceticus ADP1 accumulates wax esters and TAGs as intracellular storage lipids. We describe here the identification of a bifunctional enzyme from this bacterium exhibiting acyl-CoA:fatty alcohol acyltransferase (wax ester synthase, WS) as well as acyl-CoA:diacylglycerol acyltransferase (DGAT) activity. Experiments with a knock-out mutant demonstrated the key role of the bifunctional WS/DGAT for biosynthesis of both storage lipids in A. calcoaceticus. This novel type of long-chain acyl-CoA acyltransferase is not related to known acyltransferases including the WS from jojoba (Simmondsia chinensis), the DGAT1 or DGAT2 families present in yeast, plants, and animals, and the phospholipid:diacylglycerol acyltransferase catalyzing TAG formation in yeast and plants. A large number of WS/DGAT-related proteins were identified in Mycobacterium and Arabidopsis thaliana indicating an important function of these proteins. WS and DGAT activity was demonstrated for the translational product of one WS/DGAT homologous gene from M. smegmatis mc(2)155. The potential of WS/DGAT to establish novel processes for biotechnological production of jojoba-like wax esters was demonstrated by heterologous expression in recombinant Pseudomonas citronellolis. The potential of WS/DGAT as a selective therapeutic target of mycobacterial infections is discussed.

Acinetobacter↗

PubMed2005

Cloning and characterization a novel human 1-acyl-sn-glycerol-3-phosphate acyltransferase gene AGPAT7.

The 1-Acylglycerolphosphate acyltransferase is crucial enzyme for synthesis of glycerolipids as well as triacylglylcerol biosynthesis in eukaryotes. Six members of 1-acyl-sn-glycerol-3-phosphate acyltransferase family in human have been described, which were AGPAT1, 2, 3, 4, 5 and 6. Here we report the cloning and characterization of another novel human 1-acyl-sn-glycerol-3-phosphate acyltransferase member AGPAT7 (1-acyl-sn-glycerol-3-phosphate acyltransferase 7) gene, which was mapped to human chromosome 15q14. The AGPAT7 cDNA is 1898 bp in length, encoding a putative protein with 524 amino acid residues, which contains an acyltransferase domain in 123-234 aa. RT PCR amplification in 18 human tissues indicated that human AGPAT7 gene was widely expressed in uterus, thymus, pancreas, skeletal muscle, bladder, stomach, lung and testis. AGPAT7 protein was mainly localized to the endoplasmic reticulum (ER) in Hela cells.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗