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Results for “deacetylation”

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At least 19 recordsLinked to original sources

PubMed1979

A pathway of polygalactosamine formation in Aspergillus parasiticus: enzymatic deacetylation of N-acetylated polygalactosamine.

1. An enzyme which hydrolyzes the acetamido groups of N-acetylgalactosamine residues in N-acetylated polygalactosamine was found in the supernatant fraction of Aspergillus parasiticus AHU 7165, a polygalactosamine-producing strain. 2. N-Acetylated polygalactosamine was used as a substrate in the purification and characterization of this enzyme. A 140-fold purification was obtained by means of ammonium sulfate fractionation followed by chromatography on carboxymethylcellulose and DEAE-cellulose. 3. The enzyme releases about 60-70% of the acetyl groups of N-acetylated polygalactosamine, giving a product with free amino groups. Whereas the enzyme also deacetylates oligosaccharides with 14 or more N-acetylgalactosamine units at a rate similar to that of deacetylation of the polymer, it deacetylates shorter oligosaccharides (trimer to hexamer of N-acetylgalactosamine) much more slowly and is virtually inactive toward disaccharide. Deacetylation can not be detected with bacterial cell wall peptidoglycan, N-acetylated heparin, partially O-hydroxyethylated chitin or monomeric N-acetylgalactosamine derivatives as substrates. 4. This enzyme shows double pH optima of 5.3 and 9.3. The Km value for N-acetylated poly-galactosamine is 0.15 g/l (or 0.54 mM with respect to monosaccharide residues). 5. The occurrence of this enzyme may account for the formation of polygalactosamine with free amino groups.

Acetylgalactosamine↗

PubMed1979

Histone deacetylation in nuclei isolated from hepatoma tissue culture cells. Inhibition by sodium butyrate.

Nuclei from hepatoma tissue culture (HTC) cells were isolated by standard methods and incubated in media commonly used for nuclease digestions (DNAase I and micrococcal nuclease) and for in vitro RNA synthesis. During the incubation, histones can be deacetylated from both control cells and cells treated with 6 mM sodium butyrate to enhance the levels of histone acetylation. Deacetylation of histone is much more apparent in nuclei isolated from sodium butyrate-treated cells. Inclusion of 6 mM sodium butyrate in the incubation medium effectively inhibits the endogenous deacetylase activity acting on histones H3 and H4, whereas sodium acetate at the same concentration has very little inhibitory effect.

Acetates↗

PubMed1979

Elevation of histamine levels in rat and mouse tissues by the deacetylation of administered N-acetylhistamine.

N-Acetylhistamine administered to mice and rats (200-800 mg/kg, i.p.) elevated tissue histamine levels to a considerable extent. N-Acetylhistamine was more potent to elevate histamine than was histidine, a precursor amino acid of histamine. From the present results and the distribution of N-acetylhistamine deacetylase in tissues, it could be concluded that the elevation of histamine was due to the deacetylation of N-acetylhistamine. In addition, a slight but significant amount of N-acetylhistamine was found in tissues of normal rats. The physiological role of the deacetylation of N-acetylhistamine is discussed on the basis of these results.

Animals↗

PubMed2025

HDAC6-dependent deacetylation of SAE2 enhances SUMO1 conjugation for mitotic integrity.

Mammalian cells express three conjugatable SUMO variants: SUMO1 and the closely related SUMO2 and SUMO3 (together referred to as SUMO2/3). While some substrates are modified by both, others show a clear preference, though the basis for this selectivity remains unclear. Here, we examine a modification of the catalytic component of the human SUMO activation enzyme, SAE2. We find that lysine 164 of SAE2 undergoes HDAC6-dependent deacetylation during mitosis. A non-deacetylatable acetyl-mimetic mutant, SAE2-K164Q, selectively enhances SUMO2 over SUMO1 activation and conjugation, and distinguishes between SUMO1 and SUMO2/3 based on differences in their C-terminal tails. Complementation of SAE2-deficient or inhibited cells with SAE2-K164Q suppresses mitotic SUMO1 conjugation and promotes multipolar spindle formation. We identify NuMA as a SUMO E1-dependent substrate and demonstrate that mitotic defects caused by SAE2-K164Q or HDAC6 inhibition are rescued by SUMO1 overexpression or expression of a GFP-SUMO1-NuMA-K1766R fusion. These results support a model in which SAE1:SAE2 deacetylation during early mitosis promotes SUMO1 conjugation to ensure mitotic fidelity, highlighting a regulatory role for the SUMO-activating enzyme in the selection of SUMO proteins.

Humans↗

PubMed1977

Kinetic evidence for an intermediate in the deacetylation of monoacetyl-chymotrypsin.

Mono[14C]acetyl-chymotrypsin was prepared by treating alpha-chymotrypsin with a 10-fold molar excess of p-nitrophenyl[14C]acetate at pH 5, and the acetylated enzyme was isolated free of excess reagents by gel filtration. Deacetylation at pH 6.0 was followed by observing the decrease in acid-precipitable radioactivity and provided a first-order rate constant of 0.02 +/- 0.008 min-1. Reactivation of the acetylated protein was followed by continuously monitoring the appearance of esterolytic activity towards alpha-N-acetyltyrosine ethyl ester. Reactivation at pH 6.0 occurred exponentially with a first-order rate constant of 0.2 +/- 0.015 min-1, the reactivated enzyme exhibiting an apparent catalytic contant (k' cat) of 1200 +/- 60 min-1, which decreased to a value of 945 +/- 15 min-1 by an apparent first-order process with a rate constant of 0.025 +/- 0.006 min-1. These results are interpreted in terms of a two-step deacetylation of monoacetyl-chymotrypsin involving an acetylated intermediate with esterase activity.

Acetates↗

PubMed1976

Enzymic deacetylation of carcinogenic arylacetamides by tissue microsomes of the dog and other species.

The relative ability of arylacetamide deacetylase enzyme systems of dog liver to carry out the deacetylation of the carcinogens, 4-acetylaminobiphenyl, 2-acetylaminofluorene, and 2-acetylaminaphthalene, was examined. The arylacetamides were incubated with unfortified dog liver microsomes, and enzyme activity (nmol arylamine/mg protein/hr) was estimated by colorimetric quantitation of the resulting arylamines. The dog liver enzyme system displayed characteristics similar to those described for the rodent liver enzyme system in that enzyme activity was greatest in liver tissue, was localized in the microsomal subcellular fraction, required no cofactors, and was inhibited by heat, sodium fluoride, and thiol reagents. In five replicate assays, the relative rates of deacetylation were about 10, 6, and 1 with 4-acetylaminobiphenyl (84.8 +/- 12.4), 2-acetylaminofluorene (52.5 +/- 5.1), and 2-acetylaminonaphthalene (8.8 +/- 3.3), respectively. As a canine urinary bladder carcinogen, 4-acetylaminobiphenyl is considered more potent than 2-acetylaminofluroene, while 2-acetylaminonaphthalene is devoid of detectable carcinogenic activity, despite the fact that 2-aminoaphthalene is a well-established canine urinary bladder carcinogen. Removal of the acetyl group may be a requirement for urinary bladder carcinogenesis; accordingly, the present studies demonstrate the appearance of a direct relationship between dog liver deacetylase enzyme specificity and urinary bladder susceptibility to these carcinogenic arylacetamides.

2-Acetylaminofluorene↗

PubMed1979

Pharmacokinetics of cephalothin: accumulation of its deacetylated metabolite in uremic patients.

The pharmacokinetics of cephalothin and its deacetyl metabolite were studied with use of a chemical assay involving high-pressure liquid chromatography. In seven patients with normal renal function, the half-life of cephalothin was about 28 min and concentrations of deacetylcephalothin in serum were low. In five patients with uremia, the half-life of cephalothin averaged 221 min and there was a continuous accumulation of the deacetyl metabolite in serum during treatment. Recovery of the drug in urine was quantitative when renal function was normal, whereas the amount of drug excreted was very low in cases of uremia. The results offer some explanation of the complex pharmacokinetics of cephalothin seen with microbiological tests and illustrate the usefulness of specific chemical assays, especially in the monitoring of serum concentrations of mixtures of antibiotic compounds that differ in antibacterial activity.

Cephalothin↗

PubMed1975

Biological modification of trichothecene mycotoxins: acetylation and deacetylation of deoxynivalenols by Fusarium spp.

Attempts were made to elucidate the acetyl transformation of novel trichothecene mycotoxins, 3a,7a,15-trihydroxy-12,13-epoxytrichothec-9-en-8-one (deoxynivalenol) and its derivatives, by trichothecene-producing strains of Fusarium nivale, F. roseum, and F. solani. In the peptone-supplemented Czapek-Dox medium, F. roseum converted 3a-acetoxy-7a,15-dihydroxy-12,13-epoxytrichothec-9-en-8-one (3-acetyldeoxynivalenol) to deoxynivalenol. 3-Acetyldeoxynivalenol was also deacetylated by intact mycelia of the three strains in sugar-free Czapek-Dox medium. The growing F. nivale acetylated deoxynivalenol to afford a small amount of 3-acetyldeoxynivalenol. 3a,7a,15-Triacetoxy-12,13-epoxytrichothec-9-en-8-one (7,15-diacetyl-deoxynivalenol), which was then deacetylated to give 7a-acetoxy-3a,15-dihydroxy-12,13-epoxytrichothec-9-en-8-one (7-acetyldeoxynivalenol). It was noted that the ester at C-7 was not hydrolyzed by the fungal mycelium.

Acetylation↗

PubMed1976

Metabolic deacetylation: in vitro and in vivo studies in man, rat, dog and rhesus monkey with isomeric tetrahydroisoquinolyl derivatives of 3,4-dimethylbenzyl acetate.

The pharmacological activities of a racemic mixture of tetrahydroisoquinolyl derivatives of 3,4-dimethylbenzyl acetate, (+/-) Ro 03-4661 and the corresponding resolved isomers (+) Ro 03-4661 and (--) Ro 03-4661 have been studied in rat and rhesus monkey. The racemate and the (--) isomer showed narcotic analgesic activity by the oral route in both species. Drug metabolism studies indicated that the activity was probably due to metabolic Deacetylation to the corresponding carbinol Ro 03-4632. deacetylation did not occur in the dog, but was observed in the rat and rhesus monkey. In both these species the hydrolysis was more extensive after oral than parenteral administration. In vitro studies also showed considerable species variation in the ability of blood and tissue esterases to hydrolyse the different stereochemical isomers.

Acetylation↗

PubMed1978

Absence of evidence for an intermediate in the deacetylation of acetylchymotrypsin.

A recent paper [Chibber, B. A. K., Tomich, J. M., Mertz, E. T. & Viswanatha, T. (1977) Proc. Natl. Acad. Sci. USA 74, 510-514] presented evidence that was taken to support the existence of an intermediate in the deacetylation of acetylchymotrypsin. It was observed that deacylation, as measured by following the decrease in [(14)C]acetylchymotrypsin (decrease in acid-precipitable radioactivity), occurred at 1/10 the rate of reactivation, as measured by return of activity toward N-acetyl-L-tyrosine ethyl ester. Our experiments have shown that, at pH 6, the deacylation rate constant (measured by the loss of [(14)C]acetylchymotrypsin and by the formation of [(14)C]acetate) is identical (within experimental error) with the rate constant for reactivation (measured by determining the activity of aliquots of reactivating enzyme against N-acetyl-L-tryptophan ethyl ester) and with K(cat) for the turnover of p-nitrophenyl acetate by alpha-chymotrypsin. Part of the 10-fold greater reactivation rate observed by Chibber et al. has been shown to be due to the presence of 10% (vol/vol) isopropanol in their reactivation mixture, and it is argued that the balance of the effect is a manifestation of the "indole effect" produced by the simultaneous presence of 10 mM N-acetyl-L-tyrosine ethyl ester throughout the reactivation experiments. The results presented are entirely consistent with the three-step mechanism of catalysis by alpha-chymotrypsin and negate the existence of the proposed additional acetyl-enzyme intermediate.

Acetylation↗

PubMed1978

Butyrate suppression of histone deacetylation leads to accumulation of multiacetylated forms of histones H3 and H4 and increased DNase I sensitivity of the associated DNA sequences.

Exposure of HeLa cells to Na butyrate leads to an accumulation of multiacetylated forms of histones H3 and H4. Our studies of histone acetylation in HeLa S-3 cells show that 7 mM butyrate suppresses the deacetylation of histones without influencing the rate of radioactive acetate incorporation. An alteration in nucleosome structure in highly acetylated chromatin is indicated by an increased rate of DNA degradation by DNase I. A close association of acetylated histones with the DNase I-sensitive sequences is confirmed by the finding that histones remaining after limited DNase I digestion are depleted in the multiacetylated forms of histones H3 and H4. DNase I treatment has also been found to selectively release [3H]acetyl-labeled H3 and H4 from avian erythrocyte nuclei under conditions previously shown to preferentially degrade the globlin genes in erthyrocyte chromatin. Our results are consistent with the view that histone acetylation provides a key to the mechanism for altering chromatin structure at the nucleosomal level, and that this may explain the selective DNase I sensitivity of transcriptionally active DNA sequences in different cell types.

Acetylation↗

PubMed1975

A pathway of chitosan formation in Mucor rouxii. Enzymatic deacetylation of chitin.

1. An enzyme that catalyzes hydrolysis of acetamido groups of chitin derivatives was found in the supernatant fraction of Mucor rouxii. 2. Partially O-hydroxyethylated chitin (glycol chitin) was used as a substrate in the purification and characterization of this enzyme. A 140-fold purification was obtained by means of ammonium sulfate fractionation followed by chromatography on carboxymethylcellulose and DEAE-cellulose. 3. The enzyme releases about 30% of the acetyl groups of glycol chitin, giving a product with a decreased sensitivity to lysozyme. The enzyme also deacetylates chitin and N-acetylchitooligoses, whereas it is inactive toward bacterial cell wall peptidoglycan, N-acetylated heparin, a polymer of N-acetylgalactosamine, di-N-acetylchitobiose and monomeric N-acetylglucosamine derivatives. 4. This enzyme shows a pH optimum of 5.5. The Km value for glycol chitin is 0.87 g/l or 2.6 mM with respect to monosaccharide residues. 5. The occurrence of this enzyme accounts for the formation of chitosan in fungi.

Amidohydrolases↗

PubMed1978

Intraperiplasmic growth of Bdellovibrio bacteriovorus 109J: N-deacetylation of Escherichia coli peptidoglycan amino sugars.

During intraperiplasmic growth of Bdellovibrio bacteriovorus on Escherichia coli, the substrate cell peptidoglycan is extensively modified as it is converted to bdelloplast peptidoglycan. The initially lysozyme-sensitive peptidoglycan of E. coli was rapidly converted to a lysozyme-resistant form. The conversion was due to the N-deacetylation of a large portion of the peptidoglycan amino sugars. Chemically acetylating the isolated peptidoglycan restored its sensitivity to lysozyme digestion. However, approximately half of the products of lysozyme digestion exhibited hydrophobic interactions that were shown not to be due to the presence of protein. This suggests that a molecule capable of hydrophobic interactions, other than protein, becomes linked to the bdelloplast peptidoglycan. The data also suggest that much of the Braun lipoprotein is removed from the E. coli peptidoglycan early during bdellovibrio development.

Amidohydrolases↗

PubMed1976