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At least 19 recordsLinked to original sources
PubMed1976

Activation of long chain fatty acids with acyl carrier protein: demonstration of a new enzyme, acyl-acyl carrier protein synthetase, in Escherichia coli.

A soluble enzyme activity which catalyzes the synthesis of acyl-acyl carrier protein from acyl carrier proteins, a long chain fatty acid, and ATP has been demonstrated in E. coli. The reaction requires high concentrations of both Ca++ and Mg++ for activity, and cleaves ATP to AMP and PPi. The fatty acyl product has been identified as acyl-acyl carrier protein by its solubility, thioester linkage, molecular weight, charge, and biological activity. Several criteria indicate the enzyme is distinct from acyl-CoA synthetase. The fatty acid specificity of the enzyme suggests a role of acyl-acyl carrier protein synthetase in the incorporation of fatty acids into phospholipid.

Adenosine Triphosphate↗
PubMed1979

Synthesis of 1-palmitoyl and 1-stearoyl phosphatidylcholines from mixtures of acyl acceptors via acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in liver microsomes.

The fatty acid selectivity of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat liver microsomes was studied using a mixture of the [1-(3)H]palmitoyl plus [1-(14C)stearoyl molecular species of 1-acylglyceryl-phosphorylcholine. At a 1-acyl-sn-glycero-3-phosphorylcholine concentration of 0.16 mM, the enzyme exhibited a selectivity of 3.5-fold for the 1-palmitoyl over the 1-stearoyl species of the acyl acceptor and reaction velocities with linoleoyl- and arachidonoyl-CoA were 38--47% greater than with oleoyl-CoA. Lowering the acceptor concentration to 0.016 mM gave reaction rates with the polyenoic thiolesters which were 174--187% greater than with oleoyl-CoA and the 1-palmitoyl-sn-glycero-3-phosphorylcholine was preferred by 2.2, 1.6, and 1.6-fold with oleoyl-, linoleoyl- and arachidonoyl-CoA, respectively. The results support the potential importance of the fatty acid selectivities of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase towards both acyl acceptor and donor in regulating the phosphatidylcholine species formed by the reaction in vivo.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1975

Acylation of sn-glycerol 3-phosphate in Escherichia coli. Study of reaction with native palmitoyl-acyl carrier protein.

The sn-glycerol-3-phosphate acyltransferase activity of Escherichia coli has been assayed using native palmitoyl-acyl carrier protein as the acyl donor. This substrate was synthesized by a plant chloroplast system which utilized E. coli acyl carrier protein. The properties of the acyltransferase as assayed with palmitoyl-acyl carrier protein were similar to those observed using palmitoyl-CoA as the acyl donor. This finding suggested that single enzyme catalyzed transfer of acyl groups from either thioester to sn-glycerol 3-phosphate. This hypothesis was tested by assay of two classes of E. coli mutants which have altered sn-glycerol-3-phosphate acyltransferases. Both classes (plsA and plsB) of mutants have similarly altered activities as assayed with either palmitoyl-acyl carrier protein or palmitoyl-CoA. These results indicate that the same acyltransferase enzyme (or enzyme system) catalyzes the incorporation of both thioester substrates into phospholipid. Other experiments have shown that the acyltransferase of a plsB mutant was abnormally thermolabile only when palmitoyl-CoA was the acyl donor in the reaction. No thermolability was observed with palmitoyl-acyl carrier protein as acyl donor. The thermolability observed with palmitoyl-CoA is attributed to the detergent properties of this substrate. In agreement with Lueking and Goldfine (Lueking, D. R., and Goldfine, H. (1975) J. Biol. Chem. 250, 4911-4917), we found that guanosine-5'-diphosphate-3'-diphosphate (ppGpp) inhibits the acyltransferase only when palmitoyl-CoA was the acyl donor. No inhibition was observed when the acyltransferase was assayed with palmitoyl-acyl carrier protein in the presence of ppGpp. Incubation of the enzyme with ppGpp to assay results in a profound inhibition of acyltransfer from palmitoyl-CoA but has no effect on the incorporation of acyl groups from palmitoyl-acyl carrier protein.

Acyltransferases↗
PubMed1979

Preparative enzymatic synthesis and hydrophobic chromatography of acyl-acyl carrier protein.

We have used purified preparations of acyl-acyl carrier protein synthetase to prepare pure, native acyl-acyl carrier proteins (acyl-ACP) ranging in chain lengths from C10:0 to C delta 9 18:1. Factors affecting yield are explored and reaction conditions are presented that yield 0.8 to 0.9 mg of C16:0-ACP/ml of reaction mix. Ohter acyl groups, such as C10:0 and C delta 9 18:1 are poorer substrates and gave correspondingly lower yields. Acyl-Acp synthetase may be recovered from the reaction mixture using blue-Sepharose CL-6B and recycled. ACP and acyl-ACP are separated by hydrophobic chromatography on octyl-Sepharose CL-4B. Mixtures of acyl-ACPs could be resolved according to acyl chain length using octyl-Sepharose CL-4B columns eluted with a 2-propanol gradient. The high resolution obtained using 2-propanol gradients to separate acyl-ACP species suggests that similar techniques would be applicable to the chromatography of protein mixtures on hydrophobic supports.

Acyl Carrier Protein↗
PubMed1975

sn-Glycerol-3-phosphate acyltransferase activity in particulate preparations from anaerobic, light-grown cells of Rhodopseudomonas spheroides. Involvement of acyl thiolester derivatives of acyl carrier protein in the synthesis of complex lipids.

Crude particulate preparations obtained from anaerobic, light-grown cells of Rhodopseudomonas spheroides have been shown to possess a significant level of sn-glycerol-3-phosphate acyltransferase (EC 2.3.1.15) activity. In contrast to the enzyme from Escherichia coli, the R. spheroides glycerophosphate acyltransferase has a high specificity for acyl thiolester derivatives of acyl carrier protein (ACP) as acyl donors for the reaction. Only limited , nonlinear glycerophosphate incorporation into lipid occurs when acyl coenzyme A (CoA) derivatives are employed as acyl substrate. With oleyl-ACP as substrate, maximal enzyme activity was observed at 40 degrees, over a broad pH range (6.0 to 8.5) and did not require a divalent metal cation. The presence of dithiothreitol stimulated enzyme-activity 15 to 20%. When oleyl-ACP or palmityl-ACP was employed as sole acyl group donor, the major products recoverable from the reaction mixtures were lysophosphatidic acid, phosphatidic acid, and monoglyceride. Althouh oleyl-ACP and palmityl-ACP gave comparable maximal velocities in the initial acylation of glycerophosphate, the formation of phosphatidic acid occurred preferentially with the unsaturated acyl-ACP derivative.

Acyltransferases↗
PubMed1976

1-Hydroxy-2-tert-butyldimethylsilyl-sn-glycero-3-phosphorylcholine. A useful intermediate in the synthesis of short acyl chain 1-acyl-sn-glycero-3-phosphorylcholines.

The synthesis of 1-acyl-sn-glycero-3-phosphorylcholines in particular those containing short fatty acyl chains are described. The method involves the use of 1-acyl-2-tert-butyl-dimethylsilyl-sn-glycero-3-phosphorylcholines which can be readily prepared by reacting hens' egg yolk 1-acyl-sn-glycero-3-phosphorylcholines with tert-butyldimethylchlorosilane with imidazole as catalyst and dimethylformamide as solvent. Deacylation of the 1-acyl-2-tert-butyldimethylsilyl-sn-glycero-3-phosphorylcholines with saturated anhydrous potassium carbonate in methanol yields the 2-tert-butyldimethylsilyl-sn-glycero-3-phosphorylcholine. Reacylation of the 2-tert-butyldimethylsilyl-sn-glycero-3-phosphorylcholine with fatty acyl anhydride in the presence of 4-dimethylaminopyridine in anhydrous chloroform followed by removal of the tert-butyldimethylsilyl protecting group by treatment with dry hydrogen chloride gas in anhydrous chloroform at 0 degrees yields the desired 1-acyl-sn-glycero-3-phosphorylcholine. Various facets of the reactions involved in developing the synthetic procedures in this study are discussed.

Glycerylphosphorylcholine↗
PubMed1979

The formation of phosphatidylinositol by acylation of 2-acyl-sn-glycero-3-phosphorylinositol in rat liver microsomes.

The conversion of 2-acyl-sn-glycero-3-phosphorylinositol into phosphatidylinositol via acyl-CoA: 2-acyl-sn-glycero-3-phosphorylinositol acyltransferase activity was found to occur in rat liver microsomes. Over a wide range of conditions, stearic acid was preferred over palmitate by the acyltransferase when these acids were presented in mixtures as acyl-CoA derivatives. The potential importance of this enzyme activity for the entry of stearic acid into the 1-position of hepatic phosphatidylinositol is further supported by its greater preference for stearate relative to the acyl-CoA:2-acyl-sn-glycero-3-phosphorylcholine acyltransferase under certain assay conditions.

Acetyl-CoA C-Acyltransferase↗
PubMed1978

Acyl carrier protein from Escherichia coli: characterization by proton and fluorine-19 nuclear magnetic resonance and evidence for restricted mobility of the fatty acid chain in tetradecanoyl-acyl-carrier protein.

The acyl-carrier protein (ACP) of Escherichia coli is a protein of molecular weight 8847 with a 4'-phosphopanthetheine prosthetic group. ACP functions (via the SH of the prosthetic group) as a coenzyme in the synthesis of fatty acids and complex lipids. We report proton nuclear magnetic resonance (NMR) studies of the structure of ACP under various experimental conditions. The motion of the fatty acyl chain of acyl-ACP has been investigated by 19FNMR studies of difluorotetradecanoyl-ACP. 31PNMR studies of the prosthetic group phosphorus of ACP and acyl-ACP are also reported. We make the following conclusions: (1) the structure of ACP is stabilized by surface charge, and (2) the fatty acid residue of acyl-ACP does not move freely and seems immobilized by an interaction with the protein moiety.

Acyl Carrier Protein↗
PubMed1979

Intracellular localization of long-chain acyl-coenzyme A hydrolase and acyl-L-carnitine hydrolase in brown adipose tissue from guinea pigs.

The activities of long-chain acyl-CoA hydrolase (palmitoyl-CoA hydrolase, EC 3.1.2.2) and long-chain acyl-L-carnitine hydrolase, EC 3.1.1.28) in brown adipose tissue from cold-exposed and control guinea pigs were studied. Mitochondria from cold-exposed animals hydrolysed 21 nmol of palmitoyl-CoA/min per mg of protein and 1.3 nmol of palmitoyl-L-carnitine/min per mg of protein, and the specific activities were respectively 2 and 5 times as high in cold-exposed as in control animals. The subcellular-localization studies showed that both the long-chain acyl-CoA hydrolase and long-chain acyl-L-carnitine hydrolase were localized in the mitochondria. A location also in the soluble fraction cannot be excluded. The long-chain acyl-CoA hydrolase activity was doubled when the mitochondria were disrupted; this indicates that the enzyme is localized in the matrix compartment.

Adipose Tissue, Brown↗
PubMed1976

Identification of separate acyl- CoA:glycine and acyl-CoA:L-glutamine N-acyltransferase activities in mitochondrial fractions from liver of rhesus monkey and man.

The conjugation of glycine to benzoates and the conjugation of L-glutamine to certain arylacetates are catalyzed by two different acyl-CoA:amino acid N-acyltransferases which can be purified separately from liver mitochondrial fractions of either rhesus monkey or man. In both species, one transferase is specific for glycine and the other for L-glutamine. The glycine enzyme utilizes either butyryl-CoA or benzoyl-CoA as acyl donors while the glutamine enzyme uses either phenylacetyl-CoA or indoleacetyl-CoA. Acyl-CoA substrates for one transferase do not serve as substrates for the other. Additional studies with the monkey liver enzymes revealed that acyl-CoA substrates for one transferase inhibit the other, that the apparent Km value is low (10(-6) to 10(-5) M range) for the preferred acyl-CoA substrate as compared to the amino acid acceptor (greater than 10(-2) M) and that both transferases have a molecular weight of approximately 24,000. Hippuric acid and either phenylacetylglutamine or indoleacetylglutamine were characterized as the products formed by the separate enzymes.

Acyltransferases↗
PubMed1977

Studies on long chain cis- and trans-acyl-CoA esters and Acyl-CoA dehydrogenase from rat heart mitochondria.

The beta-oxidation of long chain fatty acids was investigated in a preparation of rat heart mitochondria. The acyl-CoA esters of the cis and trans isomers of delta9-hexadecenoic, delta9-octadecenoic, delta11-eicosenoic, and delta13-docosenoic acids were prepared. Rates of the acyl-CoA reaction were determined with an extract from rat heart mitochondria. The apparent Michaelis constant (Km) and maximum velocity (Vmax) were calculated for each substrate. In general, apparent Vmax values decreased with increasing chain length of the monoenoic substrates. Reduced activity of acyl-CoA dehydrogenase with long chain acyl-CoA esters could have contributed to accumulation of lipids in hearts of rats fed diets containing long chain fatty acids.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1978

Effect of hydrophobicity of acyl groups on the activity and stability of acylated thermolysin.

1. Normal carboxylic acids of different hydrophobicities and similar chain lengths were prepared and used for the modification of amino groups of thermolysin (EC 3.4.24.4). They were 4,7,10,13-tetraoxatetradecanoic acid, 4,7,10-trioxatetradecanoic acid, 4,7-dioxatetradecanoic acid and 4-oxatetradecanoic acid. 2. The modified enzymes were isolated by gel filtration. They had 6--7 acyl groups per molecule. Acylation of amino groups with 4-oxatetradecanoic acid and tetradecanoic acid made the enzyme insoluble. 3. The most hydrophilic enzyme derivative had similar enzyme activity and higher heat resistance than the native enzyme. The most hydrophobic derivative showed lower Km (50%) and V (40%) values for proteinase activity and lower heat resistance than the former derivative. The trioxa-derivative had intermediate characteristics. The results are discussed with respect to effects on stability and activity of the enzyme.

Acylation↗
PubMed1977

The specificity of 1-acyl-sn-glycerol 3-phosphate acyltransferase in microsomal fractions from lactating cow mammary gland towards short, medium and long chain acyl-CoA esters.

The 1-acylglycerolphosphate actyltransferase from a microsomal fraction of lactating cow mammary gland was active towards acyl-CoAs of chain length C8-C18, but not towards butyryl-CoA or hexanoyl-CoA. The lack of activity towards butyryl-CoA and hexanoyl-CoA explains why butyric and hexanoic acid are largely excluded from the sn-2 position of triacylglycerols from cow milk. The chain length specificity of the acyltransferase was C16 greater than C14 greater than C12 greater than C10 greater than C8, which is essentially the same as the order with which the fatty acids are found at the sn-2 position of cow milk triacylglycerols. The specificity was not affected by the nature of the fatty acid (palmitic or oleic acid) at the sn-1 position of 1-acylglycerolphosphate, as predicted by the theory of noncorrelative acylation.

Acyl Coenzyme A↗
PubMed1975

Beta-Ketoacyl-acyl carrier protein synthetase. Characterization of the acyl-enzyme intermediate.

Beta-Ketoacyl-acyl carrier protein (ACP) synthetase catalyzes the condensation reaction of fatty acid synthesis in Escherichia coli. The homogeneous enzyme reacts with hexanoyl-CoA to form hexanoyl-enzyme which was isolated and characterized. Hexanoyl-enzyme contains 2 mol of hexanoate/mol of enzyme (molecular weight 66,000); it is liable at alkaline pH, and it reacts with neutral hydroxylamine to form hexanoyl hydroxamic acid. Hexanoate was cleaved from the enzyme when hexanoyl-enzyme was subjected to performic acid oxidation. These properties indicate that hexanoyl-enzyme is a thioester. Studies of the circular dichroism spectra of fully acylated and nonacylated forms of the enzyme indicated that the secondary structure of the enzyme is relatively unperturbed by the presence of the hexanoyl groups. An alpha helical content of 65% was estimated for the enzyme from the circular dichroism spectrum. Hexanoyl-enzyme is active in both partial reactions that comprise the beta-ketoacyl-ACP synthetase reaction; it reacts with ACP to form hexanoyl-ACP and with malonyl-ACP to form beta-ketooctanoyl-ACP. Although the hexanoate of hexanoyl-enzyme is transferred very rapidly to ACP, the physiological acceptor in this reaction, it is also transferred very slowly to CoA, dithiothreitol, and 2-mercaptoethanol, indicating that the enzyme can react nonspecifically with a number of unrelated mercaptans.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1978

Mass spectrometry of acylated sugars as trimethylsilyl ether derivatives. A way for location of long chain fatty acyl groups.

The mass spectra of the trimethylsilyl ethers of the four positional isomers of methyl-O-palmitoyl-alpha-D-glucopyranoside have been studied, and the structures of the principal ions assigned by the use of exact mass measurements and deuterium labelling on the aliphatic chain, the trimethylsilyl group and the glucosidic methyl group. The origin of some fragments has been elucidated by analysis of reactions of metastable ions. The mass spectra of the different isomers exhibit major differences, which depend upon the presence or absence of the aliphatic chain. These results indicate that this is a useful method for determining the position of an acyl group in a methyl glucoside. The applicability of this mass spectrometric method in structural determination of unknown acylated sugars is discussed. The structure of a corynomycoloyl-alpha-D-trehalose, isolated from Corynebacterium diphtheriae, has been determined by mass spectrometry as an application of the method. The molecular weight of this compound has been determined by field desorption mass spectrometry (cationization method), and the study of the electron impact spectrum of the trimethylsilyl derivatives clearly demonstrates that the corynomycolic acid is linked by an ester group to position 6 of the trehalose molecule.

Corynebacterium diphtheriae↗