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At least 73 records · Page 4Linked to original sources
PubMed1986

The pharate adult clasper as a tool for measuring chitin synthesis and for identifying new chitin synthesis inhibitors.

A rapid, reliable, repeatable bioassay for measuring chitin synthesis is described. It utilizes the clasper from male pharate adult European corn borers and measures the incorporation of [14C]N-acetylglucosamine. Chitin synthesis is maximum in claspers taken from animals 5 and 6 days postpupation. The system is very sensitive to inhibition by the phenylbenzoyl ureas and polyoxins and should be useful for identifying potential inhibitory agents.

Acetylglucosamine↗
PubMed1997

Deacetylation of chitin oligosaccharides of dp 2-4 by chitin deacetylase from Colletotrichum lindemuthianum.

Chitin oligosaccharides of degree of polymerization 2-4 were deacetylated by purified chitin deacetylase isolated from Colletotrichum lindemuthianum to give their corresponding breakdown products after purification by liquid chromatography. Data from FABMS analyses suggested that N,N',N",N"'-tetraacetylchitotetraose and N,N',N"-triacetylchitotriose were converted into fully-deacetylated corresponding chitosan oligomers. Conversely, N,N'-diacetylchitobiose [(GlcNAc)2] was deacetylated to give a product which showed an [M + H]+ pseudomolecular ion at m/z 383, suggesting that either of the two acetyl groups were removed. Further data from 1H NMR analyses confirmed that the reaction product was 2-acetamido-4-O-(2-amino-2-deoxy-beta-D-glucopyranosyl)-2-deoxy-D-glucos e [GlcN-GlcNAc]. The enzymatic method has three advantageous characteristics over chemical methods: (i) it does not cause unexpected degradation of the sugar chain, (ii) it is highly reproducible, and (iii) unique compounds such as GlcN-GlcNAc may be produced.

Amidohydrolases↗
PubMed1991

Direct determination of acetic acid in strongly acidic hydrolysates of chitin and chitin-containing biological products by capillary gas chromatography.

Laboratory-made capillary columns with high effectiveness and inertness were used for the determination of N-acetyl groups in chitin-containing biological products by liberation of acetic acid in 4 M HCl hydrolysates. The quantitative gas chromatographic analysis is fast, requiring only 2 min, with good precision and accuracy. After a long working period of more than 1000 analyses the capillary column retained its high effectiveness and inertness.

Acetates↗
PubMed2006

Chitinase-catalyzed synthesis of alternatingly N-deacetylated chitin: a chitin-chitosan hybrid polysaccharide.

A chitin-chitosan hybrid polysaccharide (2) having a beta(1-->4)-linked alternating structure of an N-acetyl-D-glucosamine (GlcNAc) unit and a D-glucosamine (GlcN) unit was synthesized via chitinase-catalyzed polymerization of an oxazoline derivative of a GlcNbeta(1-->4)GlcNAc monomer (1). Monomer 1 was designed as a transition-state analogue substrate (TSAS) monomer for chitinase catalysis, which belongs to the glycoside hydrolase family 18. Monomer 1 was effectively polymerized by the catalysis of enzymes from Bacillus sp., Serratia marcescens and Streptomyces griseus, under weak alkaline conditions, giving rise to a water-soluble hybrid polysaccharide (2) in good yields. Molecular weights of 2 reached 2,020 with using chitinase from Serratia marcescens, which corresponds to 10-12 saccharide units.

Acetylation↗
PubMed1985

Chitinase-gold complex used to localize chitin ultrastructurally in tomato root cells infected by Fusarium oxysporum f. sp. radicis-lycopersici, compared with a chitin specific gold-conjugated lectin.

A cytochemical technique for the ultrastructural localization of chitin in tomato root cells infected by Fusarium oxysporum f. sp. radicis-lycopersici is reported. Chitinase was complexed to colloidal gold and thin sections were incubated with the enzyme-gold complex. This technique yielded a more uniform distribution of gold particles over the fungus wall, compared to that obtained with the lectin-gold technique. Both techniques revealed no labelling of the fungus cytoplasm, except for organelles resembling Woronin bodies. No significant labelling of either healthy or infected root cells was seen except for the secondary walls of vessels and, occasionally, that of adjoining parenchyma cells. The importance of this technique in studying the development of the pathogen within host cells is discussed.

Chitinases↗
PubMed1987

Two chitin synthases in Saccharomyces cerevisiae.

Disruption of the yeast CHS1 gene, which encodes trypsin-activable chitin synthase I, yielded strains that apparently lacked chitin synthase activity in vitro, yet contained normal levels of chitin (Bulawa, C. E., Slater, M., Cabib, E., Au-Young, J., Sburlati, A., Adair, W. L., and Robbins, P. W. (1986) Cell 46, 213-225). It is shown here that disrupted (chs1 :: URA3) strains have a particulate chitin synthetic activity, chitin synthase II, and that wild type strains, in addition to chitin synthase I, have this second activity. Chitin synthase II is measured in wild type strains without preincubation with trypsin, the condition under which highest chitin synthase II activities are obtained in extracts from the chs1 :: URA3 strain. Chitin synthase II, like chitin synthase I, uses UDP-GlcNAc as substrate and synthesizes alkali-insoluble chitin (with a chain length of about 170 residues). The enzymes are equally sensitive to the competitive inhibitor Polyoxin D. The two chitin synthases are distinct in their pH and temperature optima, and in their responses to trypsin, digitonin, N-acetyl-D-glucosamine, and Co2+. In contrast to the report by Sburlati and Cabib (Sburlati, A., and Cabib, E. (1986) Fed. Proc. 45, 1909), chitin synthase II activity in vitro is usually lowered on treatment with trypsin, indicating that chitin synthase II is not activated by proteolysis. Chitin synthase II shows highest specific activities in extracts from logarithmically growing cultures, whereas chitin synthase I, whether from growing or stationary phase cultures, is only measurable after trypsin treatment, and levels of the zymogen do not change. Chitin synthase I is not required for alpha-mating pheromone-induced chitin synthesis in MATa cells, yet levels of chitin synthase I zymogen double in alpha factor-treated cultures. Specific chitin synthase II activities do not change in pheromone-treated cultures. It is proposed that of yeast's two chitin synthases, chitin synthase II is responsible for chitin synthesis in vivo, whereas nonessential chitin synthase I, detectable in vitro only after trypsin treatment, may not normally be active in vivo.

Cations, Divalent↗
PubMed1994

An electron microscope and electron diffraction study of the effect of calcofluor and congo red on the biosynthesis of chitin in vitro.

The structure of chitin made in vitro by chitin synthetase was studied by electron microscopy and electron diffraction. Two different forms of chitin synthetase from the fungus Mucor rouxii were tested: chitosomes and 16 S particles. The long chitin fibrils produced by chitosomes had a high degree of crystallinity as revealed by electron diffraction. Specimen regions made of largely parallel microfibril bundles produced distinct fiber diagrams, an indication that the chitin chains were aligned along the fibril axis. Microdiffractometry of the shorter chitin crystals synthesized by 16 S particles also showed a similar alignment of chitin chains. Calcofluor and Congo red were powerful inhibitors of chitin synthetase and had profound effects on the color, macroscopic texture, electron microscopic morphology, and crystal structure of the biosynthesized chitin. Chitin made in the presence of Congo red had a bright red color; the one made in the presence of Calcofluor was strongly fluorescent and had a distinctly blue hue when illuminated by daylight. The dyes were tightly bound to the chitin and could not be removed by washing with water or ethanol. At low dye concentration, a mixture of two kinds of crystals was produced by 16 S particles: some were of the same dimensions as those made in the absence of dyes, but others were much thinner. At high dye concentration, there were only thin crystals. With increasing concentrations of Calcofluor or Congo red, the typical electron diffraction reflections of alpha-chitin, particularly the strong equatorial band at 0.466 nm became fainter and a new additional reflection centered at 0.40 nm arose as the dominant feature of the patterns. We regard the gel-like material, synthesized at highly inhibitory dye concentrations, as an apposition complex where the dye does not form part of the crystal structure of chitin and the bulk of the complex consists of molecular stacks of dye associated with nascent chitin chains or narrow chitin microfibrils.

Benzenesulfonates↗