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At least 19 recordsLinked to original sources
PubMed1980

Low density lipoprotein-activated lysolecithin acylation by human plasma lecithin-cholesterol acyltransferase. Identity of lysolecithin acyltransferase and lecithin-cholesterol acyltransferase.

There is in normal plasma an enzyme activity which converts labeled lysolecithin to lecithin by an energy-independent low density lipoprotein-activated pathway. Studies were undertaken to compare the identity of this enzyme with lecithin-cholesterol acyltransferase. During purification of the enzyme by ultracentrifugation and by chromatography on high density lipoprotein affinity column, DEAE-Sepharose column, and hydroxylapatite column, both the lysolecithin acyltransferase activity and the lecithin-cholesterol acyl transferase activity were found in the same fractions and were enriched to the same extent at each step. The final purified preparation which had 16,000- to 24,000-fold higher specific activities than starting plasma gave a single protein band on polyacrylamide gel electrophoresis and this single band contained both the activities. Also, the effects of pH, heat, and chemical inhibitors on the enzyme activities were similar. Plasma from patients with familial lecithin-cholesterol acyltransferase deficiency also lacked lysolecithin acyltransferase activity. These results indicate that a single enzyme carries out both lecithin-cholesterol acyltransferase and lysolecithin acyltransferase activities. The purified enzyme required apolipoprotein A-I for lecithin-cholesterol acyltransferase activity, but required low density lipoprotein for lysolecithin acyltransferase activity.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1987

Alpha-lecithin:cholesterol acyltransferase deficiency. Lack of both phospholipase A2 and acyltransferase activities characteristic of high density lipoprotein lecithin:cholesterol acyltransferase in fish eye disease.

The phospholipase A2 and acyltransferase activities characteristic of human plasma lecithin: cholesterol acyltransferase have been evaluated in incubation mixtures of lipoprotein depleted plasma of fish eye disease patients and autologous HDL or homologous normal HDL3. Both enzyme activities were strongly reduced as compared to those of normal controls. These findings further support the claim that fish eye disease plasma has a specific lack of high density lipoprotein lecithin:cholesterol acyltransferase (alpha-LCAT deficiency), although the cholesterol esterification of combined VLDL and LDL in such plasma proceeds at a normal rate.

Acyltransferases↗
PubMed1992

Two different allelic mutations in the lecithin-cholesterol acyltransferase gene associated with the fish eye syndrome. Lecithin-cholesterol acyltransferase (Thr123----Ile) and lecithin-cholesterol acyltransferase (Thr347----Met).

We have elucidated the genetic defect in a 66-yr-old patient with fish eye syndrome (FES) presenting with severe corneal opacities and hypoalphalipoproteinemia. The patient's plasma concentration of high density lipoprotein (HDL) cholesterol was reduced at 7.7 mg/dl (35.1-65.3 mg/dl in controls) and the HDL cholesteryl ester content was 31% (60-80% in controls); however, total plasma cholesteryl esters were similar to normal (60% of total cholesterol vs. a mean of 66% in controls). The patient's plasma cholesterol esterification rate was slightly reduced at 51 nmol/ml per h (control subjects: 61-106 nmol/ml per h), whereas lecithin-cholesterol acyltransferase (LCAT) activity, assayed using a HDL-like exogenous proteoliposome substrate, was virtually absent (0.9 nmol/ml per h vs. 25.1-27.9 nmol/ml per h in control subjects). DNA sequence analysis of the proband's LCAT gene revealed two separate C to T transitions resulting in the substitution of Thr123 with Ile and Thr347 with Met. The mutation at codon 347 created a new restriction site for the enzyme Nla III. Analysis of the patient's polymerase chain reaction-amplified DNA containing the region of the Thr347 mutation by digestion with Nla III confirmed that the proband is a compound heterozygote for both defects. The patient's daughter, who is asymptomatic despite a 50% reduction of LCAT activity, is heterozygous for the Thr123----Ile mutation. Our data indicate that the regions adjacent to Thr123 and Thr347 of LCAT may play an important role in HDL cholesterol esterification, suggesting that these regions may contain a portion of the LCAT binding domain(s) for HDL.

Aged↗
PubMed1993

The isopenicillin-N acyltransferase of Penicillium chrysogenum has isopenicillin-N amidohydrolase, 6-aminopenicillanic acid acyltransferase and penicillin amidase activities, all of which are encoded by the single penDE gene.

The isopenicillin-N acyltransferase of Penicillium chrysogenum catalyzes the conversion of the biosynthetic intermediate isopenicillin N to the hydrophobic penicillins. The isopenicillin-N acyltransferase copurified with the acyl-CoA:6-aminopenicillanic acid (6-APA) acyltransferase activity which transfers an acyl residue from acyl-CoA derivatives (e.g. phenylacetyl-CoA, phenoxyacetyl-CoA) to 6-APA. Other thioesters of phenylacetic acid were also used as substrates. An amino acid sequence similar to that of the active site of thioesterases was found in the isopenicillin-N acyltransferase, suggesting that this site is involved in the transfer of phenylacetyl residues from phenylacetyl thioesters. Purified isopenicillin-N acyltransferase also showed isopenicillin-N amidohydrolase, penicillin transacylase and penicillin amidase activities. The isopenicillin-N amidohydrolase (releasing 6-APA) showed a much lower specific activity than the isopenicillin-N acyltransferase of the same enzyme preparation, suggesting that in the isopenicillin-N acyltransferase reaction the 6-APA is not released and is directly converted into benzylpenicillin. Penicillin transacylase exchanged side chains between two hydrophobic penicillin molecules; or between one penicillin molecule and 6-APA. The penicillin amidase activity is probably the reverse of the biosynthetic acyl-CoA:6-APA acyltransferase. Four P. chrysogenum mutants deficient in acyl-CoA:6-APA acyltransferase lacked the other four related activities. Transformation of these mutants with the penDE gene restored all five enzyme activities.

Acyltransferases↗
PubMed1983

Influence of diets on acyl-CoA:cholesterol acyltransferase and on acyl-CoA:retinol acyltransferase in villous and crypt cells from rat small intestinal mucosa and in the liver.

Cholesterol and retinol are both esterified with long-chain fatty acid within the mucosal cells of the small intestine. The reactions are catalyzed by microsomal acyl-CoA:cholesterol and acyl-CoA:retinol acyltransferases (EC 2.3.1.26, and EC 2.3.1.-, respectively). To gain more insight into the physiological importance of these acyltransferases, they were studied in villous and crypt cells from rats either fasting or on diets which varied in fat and cholesterol content. Both enzymes had a higher activity in villous than in crypt cells. The activities in villous cells varied with feeding and fasting and the composition of diet when the animals were killed postprandially. Acyl-CoA:cholesterol acyltransferase activity went up upon cholesterol feeding whereas retinol acyltransferase in the mucosa was reduced by high-fat diets. The liver cholesterol acyltransferase activity varied with diet, it increased with both cholesterol and fat feeding, whereas retinol acyltransferase activity remained relatively constant. The results obtained suggest that different diets are of importance for cholesterol and retinol acyltransferase activities both in the intestinal mucosa and in the liver. The variation in activities of the two acyltransferases suggests that they may be different enzymes.

Acyltransferases↗
PubMed1990

Intraorganelle localization and substrate specificities of the mitochondrial acyl-CoA: sn-glycerol-3-phosphate O-acyltransferase and acyl-CoA: 1-acyl-sn-glycerol-3-phosphate O-acyltransferase from potato tubers and pea leaves.

The mitochondrial sn-glycerol-3-phosphate and 1-acyl-sn-glycerol-3-phosphate O-acyltransferases from potato tubers and pea leaves were investigated with respect to their intraorganelle localization, their positional and substrate specificities, and their fatty acid selectivities. In mitochondria from potato tubers both enzymes were found to be located in the outer membrane. The 1-acyl-sn-glycerol-3-phosphate O-acyltransferase of pea mitochondria showed the same intraorganelle localization whereas the sn-glycerol-3-phosphate O-acyltransferase behaved like a soluble protein of the intermembrane space. The sn-glycerol-3-phosphate O-acyltransferase of both potato and pea mitochondria used sn-glycerol-3-phosphate but not dihydroxyacetone phosphate as acyl acceptor and exclusively catalyzed the formation of 1-acyl-sn-glycerol-3-phosphate which subsequently served as substrate for the second acylation reaction at its C-2 position. Both acyltransferases of potato as well as pea mitochondria showed higher activities with acyl-CoA than with the corresponding acyl-(acyl carrier protein) thioesters. When different acyl-CoA thioesters were offered separately, the sn-glycerol-3-phosphate O-acyltransferase of potato mitochondria displayed no fatty acid specificity whereas the enzyme of pea mitochondria revealed one for saturated acyl groups. On the other hand, the mitochondrial 1-acyl-sn-glycerol-3-phosphate O-acyltransferases from both potato tubers and pea leaves were more active on unsaturated than on saturated acyl-CoA thioesters. Furthermore, these enzymes preferentially used oleoyl- and linoleoyl-CoA when they were offered in a mixture with saturated ones, although the fatty acid selectivity of the pea enzyme was less pronounced than that of the potato enzyme. The sn-glycerol-3-phosphate O-acyltransferase of potato mitochondria displayed a slight preference for saturated acyl groups.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1989

Purification and kinetic properties of lysophosphatidylinositol acyltransferase from bovine heart muscle microsomes and comparison with lysophosphatidylcholine acyltransferase.

The enzyme acyl-CoA:1-acyl-sn-glycero-3-phosphoinositol acyltransferase (LPI acyltransferase, EC 2.3.1.23) was purified approximately 11,000-fold to near homogeneity from bovine heart muscle microsomes. The purification was effected by extraction with the detergent 3-((3-cholamidopropyl)dimethylammonio)-1-propanesulfonate, followed by chromatography on Cibacron blue agarose, DEAE-cellulose, and Matrex gel green A. The isolated enzyme was a single protein of 58,000 Da as measured by polyacrylamide gel electrophoresis in the presence of dodecyl sulfate. This purification procedure also allows isolation of the related enzyme lysophosphatidylcholine (LPC) acyltransferase, which was separated from LPI acyltransferase at the final chromatographic step. The purified LPI acyltransferase exhibits an absolute specificity for LPI as the acyl acceptor. Broader specificity was found for acyl-CoA derivatives as substrates, although the preferred substrates are long-chain, unsaturated derivatives: measured reactivities were in the order arachidonoyl-CoA greater than oleoyl-CoA greater than eicosadienoyl-CoA greater than linoleoyl-CoA. Little activity was found with palmitoyl-CoA or stearoyl-CoA as potential substrates. These properties are consistent with a role of the enzyme in controlling the acyl group composition of phosphoinositides. Comparison of LPC acyltransferase and LPI acyltransferase shows that these two enzymes have distinct kinetic and physical properties and are affected differently by local anesthetics, which are potent inhibitors.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1985

Lysophosphatidylcholine acyltransferase and lysophosphatidylcholine: lysophosphatidylcholine acyltransferase in alveolar type II cells from fetal rat lung.

The specific activity of lysophosphatidylcholine acyltransferase in sonicated fetal rat lung type II cells was found to be an order of magnitude greater than that of lysophosphatidylcholine:lysophosphatidylcholine acyltransferase. The specific activity of lysophosphatidylcholine acyltransferase in sonicated fetal rat lung type II cells increases towards the end of gestation, whereas that of lysophosphatidylcholine:lysophosphatidylcholine acyltransferase does not show a change. While lysophosphatidylcholine acyltransferase in whole fetal lung homogenate is more active towards oleoyl-CoA than towards palmitoyl-CoA, the enzyme in sonicated fetal type II cells is more active towards palmitoyl-CoA. If measured with palmitoyl-CoA as acyl donor, the specific activity of lysophosphatidylcholine acyltransferase in type II cells is higher than that in whole lung during late gestation. In contrast, the specific activity of lysophosphatidylcholine:lysophosphatidylcholine acyltransferase in type II cells is lower than that in whole lung. These observations indicate that in fetal rat type II cells the deacylation-reacylation cycle is more important for the formation of dipalmitoylphosphatidylcholine than the deacylation-transacylation process.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1986

Mutants of Saccharomyces cerevisiae defective in sn-glycerol-3-phosphate acyltransferase. Simultaneous loss of dihydroxyacetone phosphate acyltransferase indicates a common gene.

Fourteen independent mutants of Saccharomyces cerevisiae defective in sn-glycerol-3-phosphate acyltransferase activity were isolated using a colony autoradiographic screening technique. All 14 mutants were similarly defective in dihydroxyacetone phosphate acyltransferase activity. The mutations were recessive and fell into a single complementation group. Tetrad analysis gave results consistent with mutations in a single nuclear gene affecting both activities. sn-Glycerol-3-phosphate acyltransferase activity from different mutant strains exhibited different substrate dependencies and differing responses to temperature, detergent, and pH. In each case, the response of the dihydroxyacetone phosphate acyltransferase activity was similar to that of the sn-glycerol-3-phosphate acyltransferase. These results are consistent with the mutations occurring in the structural gene. The data also establish that the predominant dihydroxyacetone phosphate acyltransferase activity in yeast is a second activity of the sn-glycerol-3-phosphate acyltransferase.

Acyltransferases↗
PubMed1975

Separation of 1-acylglycerolphosphate acyltransferase and 1-acylglycerolphosphorylcholine acyltransferase of rat liver microsomes.

1-Acylglycerolphosphate acyltransferase (Ec 2.3.1-) and 1-acylglycerolphosphorylcholine acyltransferase (EC 2.3.1.23) of rat liver microsomes were separated from each other. The separation was achieved by sucrose density gradient centrifugation of the enzyme preparation that was obtained by solubilizing microsomes with a nonionic detergent, Triton X-100, and subjecting the solubilized microsomes to molecular-sieve chromatography. The two acyltransferases are distinguishable from each other also with respect to their stabilities to heat and to Triton X-100. Hence, it is concluded that these acyltransferases are distinct enzymes. These results, together with our previous finding that glycerolphosphate acyltransferase is also a separate enzyme, demonstrate the presence of distinct acyltransferases responsible for the acylation of the different acyl acceptors. Furthermore, the acyl-donor specificities of these acyltransferases provide the enzymatic basis for the nonrandom distribution of fatty acids in naturally occurring glycerolipids.

Acyltransferases↗
PubMed1976

Activity of cholinephosphotransferase, lysolecithin: lysolecithin acyltransferase and lysolecithin acyltransferase in the developing mouse lung.

1. The present study presents the activity profiles of cholinephosphotransferase, lysolecithin:lysolecithin acyltransferase and lysolecithin acyltransferase at different stages of development of the mouse lung. 2. The specific activity of cholinephosphotransferase, a key enzyme in the de novo synthesis of phosphatidylcholine, increases during the later stages of fetal development until it reaches a maximal value at a gestational age of 17 days, i.e. 2 days before term. Thereafter, the activity of the enzyme declines again until around term. 2. The specific activity of lysolecithin:lysolecithin acyltransferase which catalyzes the transesterification between two molecules of 1-acyl-sn-glycero-3-phosphocholine, appears to be much lower than that of cholinephosphotransferase at gestational ages below 18 days. However, around day 18, the specific activity of lysolecithin:lysolecithin acyltransferase increases dramatically until it almost equals the maximal activity of cholinephosphotransferase measured on day 17. 4. The specific activity of lysolecithin acyltransferase, which catalyzes the direct acylation of 1-acyl-sn-glycero-3-phosphocholine, does not change significantly during the prenatal development and is lower than that of either lysolecithin:lysolecithin acyltransferase or cholinephosphotransferase at all stages of development. 5. These results are discussed in view of the possible role of these enzymes in the biosynthesis of pulmonary 1,2-dipalmitoyl-sn-glycero-3-phosphocholine.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1979

Lysolecithin acyltransferase and lysolecithin: lysolecithin acyltransferase in adult rat lung alveolar type II epithelial cells.

1. The specific activity of lysolecithin acyltransferase (EC 2.3.1.23) in sonicated adult rat lung alveolar type II epithelial cells, measured either alone or in combination with acyl-CoA synthetase (EC 6.2.1.3), was found to be an order of magnitude greater than that of lysolecithin:lysolecithin acyltransferase. 2. Lysolecithin acyltransferase in type II cells was found to prefer palmitoyl-CoA over oleoyl-CoA as substrate. The combination of lysolecithin acyltransferase and acyl-CoA synthetase was found to prefer palmitate over oleate for incorporation into phosphatidylcholine. 3. Compared to whole lung homogenate, sonicated adult rat type II cells are highly enriched in lysolecithin acyltransferase but not in lysolecithin:lysolecithin acyltransferase. 4. These observations indicate that in normal adult rat type II cells the deacylation-reacylation cycle is more important for the formation of dipalmitoyl phosphatidylcholine than the deacylation-transacylation process.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1995

A plant acyltransferase involved in triacylglycerol biosynthesis complements an Escherichia coli sn-1-acylglycerol-3-phosphate acyltransferase mutant.

The second acylation reaction in glycerolipid biosynthesis is catalyzed by an sn-1-acylglycerol-3-phosphate acyltransferase. The enzyme of Limnanthes douglasii involved in triacylglycerol synthesis has an unusual specificity for very long chain acyl groups in both of its substrates, namely acyl-CoA and sn-1-acylglycerol-3-phosphate, and causes the enrichment of erucoyl groups in the sn-2 position of the seed oil of this plant species. We have isolated a cDNA clone encoding this embryo-specific, microsomal acyltransferase via heterologous complementation of an Escherichia coli mutant deficient in sn-1-acylglycerol-3-phosphate acyltransferase activity. The open reading frame of the cDNA insert encodes a protein with a length of 281 amino acids, with three predicted membrane-spanning domains and of about 31.7 kDa. The sequence exhibits substantial sequence similarity to the sn-1-acylglycerol-3-phosphate acyltransferase of E. coli. The corresponding transcript was detectable in developing embryos but not in leaves of L. douglasii, and expression of the open reading frame in E. coli caused sn-1-acylglycerol-3-phosphate acyltransferase activity which showed properties different from those of the bacterial acyltransferase but typical of the L. douglasii enzyme involved in triacylglycerol biosynthesis.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1994

Isolation and characterisation of a maize cDNA that complements a 1-acyl sn-glycerol-3-phosphate acyltransferase mutant of Escherichia coli and encodes a protein which has similarities to other acyltransferases.

We selected cDNA plasmid clones that corrected the temperature-sensitive phenotype of Escherichia coli strain JC201, which is deficient in 1-acyl-sn-glycerol-3-phosphate acyltransferase activity. A plasmid-based maize endosperm cDNA library was used for complementation and a plasmid that enabled the cells to grow at 44 degrees C on ampicillin was isolated. Addition of this plasmid (pMAT1) to JC201 restored 1-acyl-sn-glycerol-3-phosphate acyltransferase activity to the cells. Total phospholipid labelling showed that the substrate for the enzyme, lysophosphatidic acid, accumulated in JC201 and was further metabolised to phosphatidylethanolamine in complemented cells. Membranes isolated from such cells were able to convert lysophosphatidic acid to phosphatidic acid in acyltransferase assays. The cDNA insert of pMAT1 contains one long open reading frame of 374 amino acids which encodes a protein of relative molecular weight 42,543. The sequence of this protein is most similar to SLC1, which is thought to be able to acylate glycerol at the sn-2 position during synthesis of inositol-containing lipids. Homologies between the SLC1 protein, the 1-acyl-sn-glycerol-3-phosphate acyltransferase of E. coli (PlsC) and the maize ORF were found with blocks of conserved amino acids, whose spacing was conserved between the three proteins, identifiable.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1990

Effect of albumin on acyl-CoA: lysolecithin acyltransferase, lysolecithin: lysolecithin acyltransferase and acyl-CoA hydrolase from rabbit lung.

Acyl-CoA: lysolecithin and lysolecithin: lysolecithin acyltransferases, as well as acyl-CoA hydrolase are important enzymes in lung lipid metabolism. They use amphiphylic lipids as substrates and differ in subcellular localization. In this sense, lipid-protein interactions can be an essential factor in their activity. We have studied the effect of albumin, as lipid-binding protein model, in the activities of these enzymes. Acyl-CoA hydrolase was inhibited in the presence of albumin, whereas acyl-CoA: lysolecithin acyltransferase showed a complex effect of activation depending on both albumin concentration and palmitoyl-CoA/lysolecithin molar ratio. Lysolecithin: lysolecithin acyltransferase was affected differentially on its two activities. Hydrolysis remained unaffected and transacylation was inhibited by albumin. These results are consequence of the interaction of albumin with both lipidic substrates that changes their critical micellar concentration.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1988

Molecular cloning of a phospholipid-cholesterol acyltransferase from Aeromonas hydrophila. Sequence homologies with lecithin-cholesterol acyltransferase and other lipases.

We have determined the nucleotide sequence of a gene encoding Aeromonas hydrophila phospholipid-cholesterol acyltransferase, an enzyme which shares many properties with mammalian lecithin:cholesterol acyltransferase. The derived amino acid sequence of the protein contains two regions which are homologous to the proposed active sites and binding sites of the plasma acyltransferase and to similar sequences in other interfacially acting lipolytic enzymes. The amino terminus is preceded by a typical 18 amino acid signal sequence. The protein, which is released into the culture supernatant by Aeromonas hydrophila, is confined to the periplasm of Escherichia coli.

Acyltransferases↗