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At least 19 recordsLinked to original sources
PubMed1975

Nonenzymatic acetylation of histones with acetyl phosphate and acetyl adenylate.

Nonenzymatic acetylation of calf-thymus lysine- and arginine-rich histones was demonstrated to occur when these proteins were incubated with [14C]acetyl phosphate and [14C]acetyl adenylate. The levels of acetylation depend on both pH and on reagent concentration. When acetyl [33P]phosphate and acetyl [3H]adenylate were used as reagents, we found neither histone phosphorylation nor adenylylation. Most of the radioactivity of 14C-labeled acetylated histones was recovered as Ne-acetyllysine. Furthermore, only a small amount of O-bound radioactivity was released by the 14C-labeled acetylated arginine-rich histone during treatment with hydroxylamine. Experiments on the acetylation of histones, in the presence of increasing salt concentration, gave different results for the two acetylating agents.

Acetates↗
PubMed1975

Synthesis of 9-O-acetyl- and 4,9-di-O-acetyl derivatives of the methyl ester of N-acetyl-beta-D-neuraminic acid methylglycoside. Their use as models in periodate oxidation studies.

Reaction of the methyl ester of N-acetyl-beta-D-neuraminic acid methyl glycoside with N-acetylimidazole yielded the corresponding 9-O-acetyl- and 4,9-di-O-acetyl derivatives. The structures of these compounds were confirmed by mass spectrometry and both 1H and 13C NMR spectroscopy. The compounds served as model substances in a comparative study of the rate of periodate oxidation of unsubstituted and of 9-O-acetylated-N-acetyl-neuraminic acids. This reaction was strongly hampered by the presence of the 9-O-acetyl group. The low molar absorbancy coefficient of N-acetyl-9-O-acetylneuraminic acid in the periodic acid/thiobarbituric acid assay can be explained by this retardation.

Chemical Phenomena↗
PubMedDate not supplied

[Content of N-acetyl-L-asparate, N-acetyl-L-glutamate and N-acetyl-L-aspartyl-L-glutamate in the brain of mammals at increased oxygen tension].

The contents of N-acetyl-l-asparate and N-acetyl-l-glutamate, N-acetyl-l-aspartyl-l-glutamate were studied in the brain of rats of six age groups: newborns and on the 1st, 7th, 14th, and 30th day after birth. The amount of N-acetyl-l-asparate, N-acetyl-l-glutamate and peptide in the rat brain for 30 days of the postanal life is 8, 3.5 and 14.3 times as high, respectively. Under hyperoxic the amount of peptide, N-acetyl-l-asparate and N-acetyl-l-glutamate in the brain of rats of all the examined groups decreases especially in 14-, 21- and 30-day animals.

Animals↗
PubMed1975

3-Hydroxy-3-methylglutaryl coenzyme A synthase. Evidence for an acetyl-S-enzyme intermediate and identification of a cysteinyl sulfhydryl as the site of acetylation.

Homogeneous liver 3-hydroxy-3-methylglutaryl coenzyme A synthase, which catalyzes the condensation of acetyl-CoA with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA, also carries out: (a) a rapid transacetylation from acetyl-CoA to 31-dephospho-CoA and (b) a slow hydrolysis of acetyl-CoA to acetate and CoA. Transacetylation and hydrolysis occur at 50 and 1 percent, respectively, the rate of the synthasecatalyzed condensation reaction. It appears that an acetyl-enzyme intermediate is involved in the transacetylase and hydrolase reactions of 3-hydroxy-3-methylglutaryl-CoA synthase, as well as in the over-all condensation process. Covalent binding to the enzyme of a [14C]acetyl group contributed by [1(-14)C]acetyl-CoA is indicated by migration of the [14C]acetyl group with the dissociated synthase upon electrophoresis in dodecyl sulfate-urea and by precipitation of [14C]acetyl-enzyme with trichloroacetic acid. At 0 degrees and a saturating level of acetyl-CoA, the synthase is rapidly (less than 20 s) acetylated yielding 0.6 acetyl group/enzyme dimer. Performic acid oxidation completely deacetylates the enzyme, suggesting the site of acetylation to be a cysteinyl sulfhydryl group. Proteolytic digestion of [14C]acetyl-S-enzyme under conditions favorable for intramolecular S to N acetyl group transfer quantitatively liberates a labeled derivative with a [14C]acetyl group stable to performic acid oxidation. The labeled oxidation product is identified as N-[14C]acetylcysteic acid, thus demonstrating a cysteinyl sulfhydryl group as the original site of acetylation. The ability of the acetylated enzyme, upon addition of acetoacetyl-CoA, to form 3-hydroxy-3-methylglutaryl-CoA indicates that the acetylated cysteine residue is at the catalytic site.

Acetylation↗
PubMed1979

Acetyl-coenzyme A deacylase activity in liver is not an artifact. Subcellular distribution and substrate specificity of acetyl-coenzyme A deacylase activities in rat liver.

Whole liver and isolated liver mitochondria are able to release free acetate, especially under conditions of increased fatty acid oxidation. In the present paper it is shown that rat liver contains acetyl-CoA deacylase (EC 3.1.2.1) activity (0.72mumol/min per g wet wt. of liver at 30 degrees C and 0.5mm-acetyl-CoA). At 0.5mm-acetyl-CoA 73% of total enzyme activity was found in the mitochondria, 8% in the lysosomal fraction and 19% in the postmicrosomal supernatant. Mitochondrial subfractionation shows that mitochondrial acetyl-CoA deacylase activity is restricted to the matrix space. Mitochondrial acetyl-CoA deacylase showed almost no activity with either butyryl- or hexanoyl-CoA. Acetyl-CoA hydrolase activity from purified rat liver lysosomes exhibited a very low affinity for acetyl-CoA (apparent K(m)>15mm compared with an apparent K(m) value of 0.5mm for the mitochondrial enzyme) and reacted at about the same rate with acetyl-, n-butyryl- and hexanoyl-CoA. We could not confirm the findings of Costa & Snoswell [(1975) Biochem. J.152, 167-172] according to which mitochondrial acetyl-CoA deacylase was considered to be an artifact resulting from the combined actions of acetyl-CoA-l-carnitine acetyltransferase (EC 2.3.1.7) and acetylcarnitine hydrolase. The results are in line with the concept that free acetate released by the liver under physiological conditions stems from the intramitochondrial deacylation of acetyl-CoA.

Acetyl-CoA Hydrolase↗
PubMed1975

Acetylation of procainamide in man and its relationship to isonicotinic acid hydrazide acetylation phenotype.

To assess the extent of the acetylation of procainamide (PA) to N-acetylprocainamide (NAPA) in man, and its relation to isonicotinic acid hydrazide (INH) acetylation phenotype, the following study was done. Fourteen subjects received 500 mg of PA - HCL orally. INH acetylation phenotype was determined by the serum half-life of INH after 4 mg/kg of INH orally. Each urine voided for 96 hr after procainamide was saved and levels of procainamide and NAPA measured by gas-liquid chromatography. The 14 subjects eliminated 52 plus or minus 4 percent of the dose as procainamide and 16 plus or minus 2 percent of the dose as NAPA. Four fast INH acetylators eliminated 23 plus or minus 3 percent of the dose as NAPA compared to 12 plus or minus 1 percent by the slow acetylators (p smaller than 0.05). The amount of unaltered procainamide excreted by the fast and slow INH acetylators was not significantly different, 50 plus or minus 4 percent and 53 plus or minus 4 percent, respectively. Of the total amount of drug recovered in the urine of the fast and slow INH acetylators, NAPA accounted for 32 percent and 19 percent, respectively (p smaller than 0.01). There appears to be a positive correlation between the ability to acetylate INH and the ability to acetylate procainamide.

Acetylation↗
PubMed1977

Ganglioside GM2 N-acetyl-beta-D-galactosaminidase and asialo GM2 (GA2) N-acetyl-beta-D-galactosaminidase; studies in human skin fibroblasts.

Ganglioside GM2 and its asialo-derivative, GA2 were radiolabeled in their N-acetyl-D-galactosaminyl moieties by oxidation with galactose oxidase and reduction with tritiated sodium borohydride. Specific activities of 6 X 10(4) dpm/nmol (GM2) and 1.8 X 10(6) dpm/nmol (GA2) were achieved. About 98% of the label was in N-acetyl-D-galactosamine. Using these substrates, an assay was developed for GM2-N-acetyl-beta-D-galactosaminidase (E.C.3.2.1.30) and GA2-N-acetyl-beta-D-galactosaminidase (E.C.3.2.1.30) activities in human cultured skin fibroblasts. The products of the GM2 cleaving reaction were identified as N-acetylgalactosamine and ganglioside GM3. Both GM2 and GA2 cleaving activities were stimulated about 5-fold by purified sodium taurocholate, and this stimulation was inhibited by neutral detergents, lipids and albumin at low concentrations. Addition of various salts, reducing agents and a protein activator factor from human liver of Li et al. (1973) did not stimulate GM2-N-acetyl-beta-D-galactosaminidase activity beyond that found with sodium taurocholate. Under optimal conditions, control fibroblast supernates cleaved ganglioside GM2 at a rate of 3.7 nmol/mg protein/h compared to 1100 for GA2-N-acetyl-beta-D-galactosaminidase and 4700 for 4-methylumbelliferyl-N-acetyl-beta-D-glucosaminidase. Supernates from two patients with Tay-Sachs disease had markedly reduced activity levels for GM2-N-acetyl-beta-D-galactosaminidase but not for the other two substrates. Supernates from two patients with Sandhoff's disease had reduced activities for all three substrates. A supernate from one patient with juvenile GM2 gangliosidosis cleaved GM2 at a somewhat faster rate than those from Tay-Sachs or Sandhoff's patients. Two healthy adult women with markedly reduced hexosaminidase A activities using 4MU-N-acetyl-beta-D-glucosaminide as substrate had approximately half-normal activities using GM2 as substrate. A patient with the Tay-Sachs phenotype but with a partial deficiency of hexosaminidase A using the 4-MU substrate had a profound deficiency using GM2 as substrate. In such unusual hexosaminidase mutants, assays using GM2 as substrate are better indicators of phenotype than those using synthetic substrates.

Adult↗
PubMed1975

Acetyl-coenzyme A hydrolase, an artifact? The conversion of acetyl-coenzyme A into acetate by the combined action of carnitine acetyltransferase and acetylcarnitine hydrolase.

1. The nature of the acetyl-CoA hydrolase (EC 3.1.2.1) reaction in rat and sheep liver homogenates was investigated. 2. The activity determined in an incubated system was 5.10 and 3.28nmol/min per mg of protein for rat and sheep liver homogenate respectively. This activity was not affected by the addition of l-carnitine, but was decreased by the addition of d-carnitine. 3. No acetyl-CoA hydrolase activity could be detected in rat or sheep liver homogenates first treated with Sephadex G-25. This treatment decreased the carnitine concentrations of the homogenates to about one-twentieth. Subsequent addition of l-carnitine, but not d-carnitine, restored the apparent acetyl-CoA hydrolase activity. 4. Sephadex treatment did not affect acetyl-carnitine hydrolase activity of the homogenates, which was 5.8 and 8.1nmol/min per mg of protein respectively for rat and sheep liver. 5. Direct spectrophotometric assay of acetyl-CoA hydrolase, based on the reaction of CoA released with 5,5'-dithiobis-(2-nitrobenzoic acid), clearly demonstrated that after Sephadex treatment no activity could be measured. 6. Carnitine acetyltransferase (EC 2.3.1.7) activity measured in the same assay system in response to added l-carnitine was very low in normal rat liver homogenates, owing to the apparent high acetyl-CoA hydrolase activity, but was increased markedly after Sephadex treatment. The V(max.) for this enzyme in rat liver homogenates was increased from 3.4 to 14.8nmol/min per mg of protein whereas the K(m) for l-carnitine was decreased from 936 to 32mum after Sephadex treatment. 7. Acetyl-CoA hydrolase activity could be demonstrated in disrupted rat liver mitochondria but not in separated outer or inner mitochondrial membrane fractions. Activity could be demonstrated after recombination of outer and inner mitochondrial membrane fractions. The outer mitochondrial membrane fraction showed acetylcarnitine hydrolase activity and the inner mitochondrial membrane fraction showed carnitine acetyltransferase activity. 8. The results presented here demonstrate that acetyl-CoA hydrolase activity in rat and sheep liver is an artifact and the activity is due to the combined activity of carnitine acetyltransferase and acetylcarnitine hydrolase.

Acetyl Coenzyme A↗
PubMedDate not supplied

N-acetylation of drugs. Pharmacogenetic studies in rabbits selected for their acetylator characteristics.

Studies on acetylation of sulfadiazine, isoniazid, and p-aminobenzoic acid in selected lines of slow and rapid acetylator rabbits are described. Pedigree analysis of rabbits classified as slow or rapid sulfadiazine acetylators confirmed previous studies that the rate of sulfadiazine elimination (acetylation) is genetically controlled, with rapid elimination dominant over slow elimination of the drug. Pharmacokinetic studies in rabbits of specified sulfadiazine acetylator genotypes with isoniazid and p-aminobenzoic acid show that the rate of isoniazid elimination is under the same genetic control as is sulfadiazine, whereas the rate of p-aminobenzoic acid elimination is not. A new drug acetylation polymorphism, which controls the rate of enzymatic acetylation of p-aminobenzoic acid in peripheral blood cells and which is related to the sulfadiazine acetylation polymorphism, is described.

Acetyltransferases↗
PubMed1979

Comparative immunogenicity of vaccines prepared from capsular polysaccharides of group C Neisseria meningitidis O-acetyl-positive and O-acetyl-negative variants and Escherichia coli K92 in adult volunteers.

Three structurally and antigenically similar capsular polysaccharides, two derived from group C Neisseria meningitidis (O-acetyl-positive and O-acetyl-negative variants) and one from Escherichia coli K92, which cross-reacts with polysaccharide from group C N. meningitidis, were compared for their ability to induce anticapsular and bactericidal antibodies to group C N. meningitidis in adult volunteers. All three vaccines elicited group C-specific serum antibodies. The vaccine derived from the O-acetyl-negative variant was the most immunogenic of the three vaccines. With use of radiolabeled O-acetyl-positive group C N. meningitidis polysaccharide antigen, the geometric mean titers of antibody in serum were 41.7 microgram/ml to the O-acetyl-negative variant, 22.8 microgram/ml to the O-acetyl-positive variant, and 7.1 microgram/ml to E. coli K92. Antibodies induced by all three vaccines were bactericidal for both of the group C N. meningitidis polysaccharide variants. An inverse relation between the comparative immunogenicity of the O-acetyl-negative polysaccharide and the virulence of group C N. meningitidis was found.

Adult↗
PubMed1977

Substrate-inhibiton by acetyl-CoA in the condensation reaction between oxaloacetate and acetyl-CoA catalyzed by citrate synthase from pig heart.

Deviations from Michealis-Menten kinetics in the pig-heart citrate synthase (citrate-oxaloacetate-lyase(pro-3S-CH2-COO-leads to acetyl-CoA), EC 4.1.3.7) system have been characterized and analyzed in view of the kinetic theory described in the preceding paper. The enzymic condensation reaction between acetyl-CoA and oxaloacetate is subject to substrate-inhibition by acetyl-CoA. This can be attributed to the formation of a productive enzyme-acetyl-CoA complex with a dissociation constant of 110 uM. The binding of acetyl-CoA to the enzyme decreases the on-velocity constant for oxaloacetate-binding from 4000 min-1- micrometer-1 to 1700 min-1-micrometer-1. The affinity of citrate synthase for oxaloacetate increase at least 20-fold on the binding of acetyl-CoA. The latter cooperativity effect can be attributed to a more than 45-fold decrease of the off-velocity constant for oxaloacetate-binding.

Acetyl Coenzyme A↗
PubMed1977

Facile synthesis of 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-D-glycopyranosyl)-alpha-D-glucopyrano-[2',1':4,5]-2-oxazolines, key intermediates for the synthesis of oligosaccharides.

A simple synthesis of disaccharide oxazolines has been developed. Condensation of methyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide, followed by removal of the 4,6-O-benzylidene group from the resulting disaccharide derivative, gave crystalline methyl 2-acetamido-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucpyranoside which, on acetolysis with acetic anhydride-acetic acid-sulfuric acid, provided 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucopyrano]-[2',1':4,5]-2-oxazoline (7). Synthesis of the related alpha-D-mannopyranosyl compound was similarly accomplished. The glycosylating capability of 7 was employed for the synthesis of 6-(benzyloxycarbonylamino)hexyl-2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside (18). An alternative synthesis of compound 18 is also described.

Glycosides↗
PubMed1976

[Excretion of acetyl urea in milk following oral 14C-acetyl urea administration to dairy cows].

2 experimental cows were fed acetyl urea several weeks before the trial was started. The first cow received a daily amount of 200 g and the second cow 855 g. On the first day of experiment both cows were given 5 mCi of 14C acetyl urea intraruminally. Up to 6 hrs after the beginning of the experiment acetyl urea in blood plasma was shown to contain a higher proportion of 14C activity than urea. 0.21 g urea and 0.18 g acetyl urea were contained in 1 kg of milk from cow No 1 while 1 kg of milk from cow No 2 contained 0.18 g urea and 0.12 g acetyl urea. The feeding of acetyl urea to dairy cows is not recommended on the basis of the fact that any further contamination of human nutrition with foreign substances should be possibly avoided.

Animal Feed↗
PubMed1978

Cardiac effects of 16-acetyl-gitoxin, the active glycoside after penta-acetyl-gitoxin administration.

The inotropic and arrhythmogenic effects of 16-acetyl-gitoxin and digoxin were studied in isolated cardiac preparations and in anaesthetized dogs. ECG alteration-producing and lethal doses of both glycosides were determined in anaesthetized cats. In the isolated guinea-pig atrium, the properties of 16-acetyl-gitoxin are identical with those of ouabain, and in the isolated guinea-pig heart they are equal to those of digoxin, while gitoxin and penta-acetyl-gitoxin produce equieffective reactions at higher glycoside concentrations. In the cat, 75% of lethal doses of 16-acetyl-gitoxin and digoxin provoke ECG changes (qrs complex prolongation). The ratio of the lethal doses amounts to 1:2.8 and 1:3.5 (digoxin:16-acetyl-gitoxin). In case of equal contractile increment, the ratio of glycoside doses in dogs amounts to 1:1.3, while the percentages of rhythm disturbances following both glycosides are identical. Apart from slight deviations of the doses used, the cardiac properties of 16-acetyl-gitoxin are equal to those of digoxin.

Acetyldigoxins↗
PubMed1977

Acetylation of prostaglandin synthetase by aspirin. Purification and properties of the acetylated protein from sheep vesicular gland.

We previously presented evidence that aspirin (acetylsalicylic acid) inhibits prostaglandin synthetase by acetylating and active site of the enzyme. In the current work, we have labeled the enzyme from an aceton-pentane powder of sheep vesicular gland using [acetyl-3H]aspirin and purified the [3H]acetyl-protein to near homogeneity. The final preparation contains protein of a single molecular weight (85 000) and an amino-terminal sequence of Asp-Ala-Gly-Arg-Ala. The [3H]acetyl-protein contained 0.5 mol of acetyl residues per mol of protein based on amino acid composition but only a single sequence was found.

Acetylation↗
PubMed1977

Des-Nalpha-acetyl-alpha-melanotropin: a synthetic substrate for specific N-terminal directed enzymatic acetylation.

Application of the 2-methylsulfonylethyloxycarbonyl group for temporary amino protection enables the synthesis from one precursor of des-Nalpha1-acetyl-alpha-MSH, the two mono N-acetylated forms (in positions I and II) and the diacetyl form of this tridecapeptide amideq The free tridecapeptide amide, although structurally unrelated to the normal substrate, was recognized by an enzyme occurring in calf eye-lens tissue. The product of the enzymatic reaction was exclusively alpha-MSH. Partial sequences derived from the N-terminus were less rapidly acetylated or not at all, depending on their chain length. The enzyme, therefore, appears to direct its activity to free N-terminal alpha-amino groups of peptides exceeding a certain critical chain length. Acetylation of epsilon-amino functions did not occur.

Acetylation↗