Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chitin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed2003

Class V chitin synthase determines pathogenesis in the vascular wilt fungus Fusarium oxysporum and mediates resistance to plant defence compounds.

Chitin, a beta-1,4-linked polysaccharide of N-acetylglucosamine, is a major structural component of fungal cell walls. Fungi have multiple classes of chitin synthases that catalyse N-acetylglucosamine polymerization. Here, we demonstrate the requirement for a class V chitin synthase during host infection by the vascular wilt pathogen Fusarium oxysporum. The chsV gene was identified in an insertional mutagenesis screen for pathogenicity mutants. ChsV has a putative myosin motor and a chitin synthase domain characteristic of class V chitin synthases. The chsV insertional mutant and a gene replacement mutant of F. oxysporum display morphological abnormalities such as hyphal swellings that are indicative of alterations in cell wall structure and can be partially restored by osmotic stabilizer. The mutants are unable to infect and colonize tomato plants or to grow invasively on tomato fruit tissue. They are also hypersensitive to plant antimicrobial defence compounds such as the tomato phytoanticipin alpha-tomatine or H2O2. Reintroduction of a functional chsV copy into the mutant restored the growth phenotype of the wild-type strain. These data suggest that F. oxysporum requires a specific class V chitin synthase for pathogenesis, most probably to protect itself against plant defence mechanisms.

Chitin Synthase↗
PubMed2001

Inhibitory activity for chitin synthase II from Saccharomyces cerevisiae by tannins and related compounds.

In the course of search for potent inhibitors of chitin synthase II from natural resources, seven tannins and related compounds were isolated from the aerial part of Euphorbia pekinensis and identified as gallic acid (1), methyl gallate (2), 3-O-galloyl-(-)-shikimic acid (3), corilagin (4), geraniin (5), quercetin-3-O-(2"-O-galloyl)-beta-D-glucoside (6), and kaempferol-3-O-(2"-O-galloyl)-beta-D-glucoside (7). These and nine related compounds, (-)-quinic acid (8), (-)-shikimic acid (9), ellagic acid (10), kaempferol (11), quercetin (12), quercitrin (13), rutin (14), quercetin-3-O-(2"-O-galloyl)-beta-D-rutinoside (15) and 1,3,4,6-tetra-O-galloyl-beta-D-glucose (16), were evaluated for the inhibitory activity against chitin synthase II and III. They inhibited chitin synthase II with IC(50) values of 18-206 microM, except for two organic acids, (-)-quinic acid (8) and (-)-shikimic acid (9). Among them, 3-O-galloyl-(-)-shikimic acid (3) was the most potent inhibitor against chitin synthase II of Saccharomyces cerevisiae with an IC(50) value of 18 microM. The inhibition appears to be selective for chitin synthase II, as they did not appreciably inhibit chitin synthase III.

Antifungal Agents↗
PubMed1975

Chitin synthetase zymogen is attached to the yeast plasma membrane.

Pretreatment of yeast protoplasts with concanavalin A, according to the method used by G. A. Scarborough for Neurospora (J. Biol. Chem. 250, 1106-1111, 1975), reinforced the plasma membranes, and helped to maintain their integrity during subsequent lysis of the protoplasts. After purification by centrifuging on a Renografin density gradient, practically intact membranes were obtained. Previous labeling of the protoplasts with 125I or with [3H]concanavalin A resulted in recovery of the radioactivity in the membrane fraction. The bulk of the chitin synthetase (chitin synthase; UDP-2-acetamido-2-deoxy-D-glucose:chitin 4-beta-acetamidodeoxyglucosyltransferase; EC 2.4.1.16) recovered in the gradient was also found In this fraction; in the zymogen form. About 20% of the activity sedimented in a plasma-membrane-free fraction at lower density. Glutaraldehyde inactivated chitin synthetase when it was added to a lysate, but not when applied to intact protoplasts. It is concluded that chitin synthetase is so oriented in the membrane that it is only accessible from the inside of the cell. These results confirm our previous hypothesis that the chitin synthetase zymogen is associated with the plasma membrane, a basic assumption for the explanation of localized activation of the enzyme and initiation of septum formation.

Cell Fractionation↗
PubMed1981

Effects of amphotericin B, nystatin, and other polyene antibiotics on chitin synthase.

The effects of amphotericin B (AmB), nystatin, filipin, and pimaricin were tested chitin synthase (EC 2.4.1.16) (chitosomes from yeast cells of Mucor rouxii). AmB and nystatin inhibited the enzyme at concentrations greater than or equal to 10 micrograms/ml, filipin was weakly inhibitory, and pimaricin had no effect. The inhibition of chitin synthase by AmB appears to be noncompetitive, with a Ki value of about 0.13 mM. the effect of nystatin was more complex and included a sharp stimulation of chitin synthase activity at approximately 50 micrograms/ml. Our findings suggest the existence of binding sites (sterols?) on the chitosome that are selective for certain polyenes and that play a role in the operation of chitin synthase. Because the minimal growth inhibitory concentrations of AmB or nystatin are lower than the concentrations that inhibit chitin synthase in vitro, the possibility of chitosomal chitin synthase being a primary target for the antifungal action of these polyenes seems unlikely.

Amphotericin B↗
PubMed1988

Chitin synthase 2 is essential for septum formation and cell division in Saccharomyces cerevisiae.

Previous work led to the puzzling conclusion that chitin synthase 1, the major chitin synthase activity in Saccharomyces cerevisiae, is not required for synthesis of the chitinous primary septum. The mechanism of in vivo synthesis of chitin has now been clarified by cloning the structural gene for the newly found chitin synthase 2, a relatively minor activity in yeast. Disruption of the chitin synthase 2 gene results in the loss of well-defined septa and in growth arrest, establishing that the gene product is essential for both septum formation and cell division.

Cell Division↗
PubMed1994

Chitin synthase 3 from yeast has zymogenic properties that depend on both the CAL1 and the CAL3 genes.

In previous studies, chitin synthase 3 (Chs3), the enzyme responsible for synthesis of most of the chitin present in the yeast cell, was found to be inactivated by incubation with trypsin, in contrast to other yeast chitin synthases (Chs1 and Chs2), which are stimulated by this treatment (chitin synthase; UDP-N-acetyl-D-glucosamine:chitin 4-beta-N-acetylglucosaminyl-transferase, EC 2.4.1.16). It has now been found that the substrate UDPGlcNAc protects Chs3 against proteolytic inactivation. Treatment of Chs3-containing membranes with detergents drastically reduced the enzymatic activity. Activity could, however, be restored by subsequent incubation with trypsin or other proteases in the presence of UDPGlcNAc. Under such conditions, protease treatment stimulated activity as much as 10-fold. A change in divalent cation specificity after trypsin treatment suggests that the protease directly affects the enzyme molecule. Experiments with mutants in the three genes involved in Chs3 activity--CAL1, CAL2, and CAL3--showed that only CAL1 and CAL3 are required for the protease-elicited (zymogenic) activity. It is concluded that Chs3 is a zymogen and that the CAL2 product functions as its activator. The differences and possible similarities between Chs3 and the other chitin synthases are discussed.

Chitin Synthase↗
PubMed1996

The chitin catabolic cascade in the marine bacterium Vibrio furnissii. Molecular cloning, isolation, and characterization of a periplasmic chitodextrinase.

Chitin catabolism in Vibrio furnissii comprises several signal transducing systems and many proteins. Two of these enzymes are periplasmic and convert chitin oligosaccharides to GlcNAc and (GlcNAc)2. One of these unique enzymes, a chitodextrinase, designated EndoI, is described here. The protein, isolated from a recombinant Escherichia coli clone, exhibited (via SDS-polyacrylamide gel electrophoresis) two enzymatically active, close running bands ( approximately mass of 120 kDa) with identical N-terminal sequences. The chitodextrinase rapidly cleaved chitin oligosaccharides, (GlcNAc)4 to (GlcNAc)2, and (GlcNAc)5,6 to (GlcNAc)2 and (GlcNAc)3. EndoI was substrate inhibited in the millimolar range and was inactive with chitin, glucosamine oligosaccharides, glycoproteins, and glycopeptides containing (GlcNAc)2. The sequence of the cloned gene indicates that it encodes a 112,690-kDa protein (1046 amino acids). Both proteins lacked the predicted N-terminal 31 amino acids, corresponding to a consensus prokaryotic signal peptide. Thus, E. coli recognizes and processes this V. furnissii signal sequence. Although inactive with chitin, the predicted amino acid sequence of EndoI displayed similarities to many chitinases, with 8 amino acids completely conserved in 10 or more of the homologous proteins. There was, however, no "consensus" chitin-binding domain in EndoI.

Acetylglucosamine↗
PubMed2003

Structural basis for new pattern of conserved amino acid residues related to chitin-binding in the antifungal peptide from the coconut rhinoceros beetle Oryctes rhinoceros.

Scarabaecin isolated from hemolymph of the coconut rhinoceros beetle Oryctes rhinoceros is a 36-residue polypeptide that has antifungal activity. The solution structure of scarabaecin has been determined from twodimensional 1H NMR spectroscopic data and hybrid distance geometry-simulated annealing protocol calculation. Based on 492 interproton and 10 hydrogen-bonding distance restraints and 36 dihedral angle restraints, we obtained 20 structures. The average backbone root-mean-square deviation for residues 4-35 is 0.728 +/- 0.217 A from the mean structure. The solution structure consists of a two-stranded antiparallel beta-sheet connected by a type-I beta-turn after a short helical turn. All secondary structures and a conserved disulfide bond are located in the C-terminal half of the peptide, residues 18-36. Overall folding is stabilized by a combination of a disulfide bond, seven hydrogen bonds, and numerous hydrophobic interactions. The structural motif of the C-terminal half shares a significant tertiary structural similarity with chitin-binding domains of plant and invertebrate chitin-binding proteins, even though scarabaecin has no overall sequence similarity to other peptide/polypeptides including chitin-binding proteins. The length of its primary structure, the number of disulfide bonds, and the pattern of conserved functional residues binding to chitin in scarabaecin differ from those of chitin-binding proteins in other invertebrates and plants, suggesting that scarabaecin does not share a common ancestor with them. These results are thought to provide further strong experimental evidence to the hypothesis that chitin-binding proteins of invertebrates and plants are correlated by a convergent evolution process.

Amino Acid Sequence↗
PubMed2006

Identification of the substrate interaction region of the chitin-binding domain of Streptomyces griseus chitinase C.

Chitinase C from Streptomyces griseus HUT6037 was discovered as the first bacterial chitinase in family 19 other than chitinases found in higher plants. Chitinase C comprises two domains: a chitin-binding domain (ChBD(ChiC)) for attachment to chitin and a chitin-catalytic domain for digesting chitin. The structure of ChBD(ChiC) was determined by means of 13C-, 15N-, and 1H-resonance nuclear magnetic resonance (NMR) spectroscopy. The conformation of its backbone comprised two beta-sheets composed of two and three antiparallel beta-strands, respectively, this being very similar to the backbone conformations of the cellulose-binding domain of endoglucanase Z from Erwinia chrysanthemi (CBD(EGZ)) and the chitin-binding domain of chitinase A1 from Bacillus circulans WL-12 (ChBD(ChiA1)). The interaction between ChBD(ChiC) and hexa-N-acetyl-chitohexaose was monitored through chemical shift perturbations, which showed that ChBD(ChiC) interacted with the substrate through two aromatic rings exposed to the solvent as CBD(EGZ) interacts with cellulose through three characteristic aromatic rings. Comparison of the conformations of ChBD(ChiA1), ChBD(ChiC), and other typical chitin- and cellulose-binding domains, which have three solvent-exposed aromatic residues responsible for binding to polysaccharides, has suggested that they have adopted versatile binding site conformations depending on the substrates, with almost the same backbone conformations being retained.

Amino Acid Sequence↗
PubMed1994

Subcellular localization, abundance and stability of chitin synthetases 1 and 2 from Saccharomyces cerevisiae.

The existence of more than one chitin synthetase in fungal cells poses the question of whether these enzymes have similar or different localization. The subcellular distribution of chitin synthetases 1 and 2 (Chs1 and Chs2) was determined in cell-free extracts of Saccharomyces cerevisiae fractionated by sucrose density gradient sedimentation. Chs1 was examined in two strains: ATCC 26109, a wild-type strain, and D3C (MAT alpha ura3-52). Chs2 was investigated in a strain (D3B) freed of Chs1 by gene disruption (MATa his4 ura3-52 chs1::URA3). A prolonged, strong centrifugation (20 h at 265000 g) was necessary to cleanly resolve two major populations of chitin synthetase particles: chitosomes (a population of microvesicles of low buoyant density, d = 1.15 g ml-1) and plasma membrane (a population of vesicles of high buoyant density, d = 1.21 g ml-1). Chs1 and Chs2 were both present in chitosomes and plasma membrane, but the relative distribution of each chitin synthetase in these two membranous populations varied. Chs2 was much less abundant than Chs1 and required Co2+ rather than Mg2+ as a cofactor. A salient finding was the high sensitivity of chitosomal Chs2 to high centrifugal forces. The subcellular distribution of 1,3-beta-glucan synthetase was the same in the three strains studied, i.e. unaffected by the presence or absence of Chs1. Culture conditions affected the profiles of chitin and glucan synthetases: the relative abundance of Chs1 in chitosomes or plasma membrane was quite different in cells grown on two different media but the buoyant density was not affected; in contrast, there was shift in the buoyant density of the two peaks of 1,3-beta-glucan synthetase. We concluded that the subcellular localization of Chs1 and Chs2 remains the same despite genetic and other differences in the properties of these enzymes. We confirmed that 1,3-beta-glucan synthetase and chitin synthetase exhibit a partially different subcellular distribution-an indication that these two enzymes are mobilized through different secretory pathways.

Centrifugation, Density Gradient↗
PubMed1999

Multiple genes involved in chitin degradation from the marine bacterium Pseudoalteromonas sp. strain S91.

A cluster of three closely linked chitinase genes organized in the order chiA, chiB and chiC, with the same transcriptional direction, and two unlinked genes, chiP and chiQ, involved in chitin degradation in Pseudoalteromnas sp. strain S91 were cloned, sequenced and characterized. The deduced amino acid sequences revealed that ChiA, ChiB and ChiC exhibited similarities to chitinases belonging to family 18 of the glycosyl hydrolases while ChiP and ChiQ belonged to family 20. ChiP and ChiQ showed different enzymic activities against fluorescent chitin analogues, but neither was able to degrade colloidal chitin. ChiA possessed chitinase activity but did not bind chitin; ChiB bound chitin but had no chitinase activity; ChiC possessed strong chitinase activity and also bound chitin. Production of ChiC in S91 appeared to be controlled by chiA expression, since insertion of a transposon into the ORF of chiA resulted in the loss of chitinase activity as well as loss of ChiC proteins in a chitinase-negative mutant. In Escherichia coli, ChiC appeared to be expressed from its own promoter.

Acetylglucosaminidase↗
PubMed2006

Treatment with chitin microparticles is protective against lung histopathology in a murine asthma model.

BACKGROUND: Chitin, a natural polysaccharide extracted from shrimp, is a potent T and B cell adjuvant when delivered in the form of chitin microparticles and can shift a polarized T-helper type 2 (Th2) immune response towards a Th1 response. OBJECTIVE: We investigated the beneficial effects of the intranasal application of chitin microparticles in newborn mice before and after the establishment of a model of allergic asthma. METHODS: Mice were grouped as asthma (A), primary prevention (PP), treatment (T), primary prevention+treatment (PPT) and control (C) groups. All mice except controls were sensitized with ovalbumin intraperitoneally and challenged intratracheally to establish the asthma model. Mice in the PP and PPT groups received chitin microparticles intranasally during the newborn period before sensitization. Mice in the PPT and T groups received intranasal chitin microparticles after challenge. Airway histopathology was evaluated in all groups. RESULTS: All of the airway histopathologic parameters of small and medium-sized airways of the T and PPT groups were significantly ameliorated when compared with the asthma model group. In the large airways, thicknesses of basement membrane, epithelium and subepithelial smooth muscle layers of the PPT group and basement membrane thicknesses of the T group were also significantly lower compared with the asthma model group. Comparison of the PP group with the asthma model group revealed significantly reduced goblet cell numbers and significantly reduced epithelial and basement membrane thicknesses in small and medium airways, in addition to significantly reduced basement membrane thicknesses in the medium-sized airways. CONCLUSION: Intranasal application of microgram quantities of chitin microparticles had a beneficial effect in preventing and treating histopathologic changes in the airways of asthmatic mice.

Administration, Intranasal↗
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↗
PubMed1999

Isolation of csm1 encoding a class V chitin synthase with a myosin motor-like domain from the rice blast fungus, Pyricularia oryzae.

A gene encoding a chitin synthase with a myosin motor-like domain (csm1) was isolated from Pyricularia oryzae using a PCR fragment amplified from a fungal chitin synthase conserved region. The deduced amino acid sequence of csm1 is homologous to that of CsmA of Aspergillus nidulans (65% identity). The putative gene product of csm1 is consisted of the myosin motor-like domain and a chitin synthase domain as in A. nidulans csmA. The chitin synthase domain of its C-terminus was also homologous to Aspergillus fumigatus ChsE (61.4% identity) and Ustilago maydis Chs6 (48.6% identity) that encode class V chitin synthases. Northern analysis demonstrated that the csm1 was expressed throughout the mycelial growth of P. oryzae. This is the first report on the isolation of the gene encoding a class V chitin synthase with the myosin motor-like domain from P. oryzae.

Amino Acid Sequence↗
PubMed1981

Chitin: New facets of research.

Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.

Animal Feed↗
PubMed1994

Nucleotide sequence variation of chitin synthase genes among ectomycorrhizal fungi and its potential use in taxonomy.

DNA sequences of single-copy genes coding for chitin synthases (UDP-N-acetyl-D-glucosamine:chitin 4-beta-N-acetylglucosaminyltransferase; EC 2.4.1.16) were used to characterize ectomycorrhizal fungi. Degenerate primers deduced from short, completely conserved amino acid stretches flanking a region of about 200 amino acids of zymogenic chitin synthases allowed the amplification of DNA fragments of several members of this gene family. Different DNA band patterns were obtained from basidiomycetes because of variation in the number and length of amplified fragments. Cloning and sequencing of the most prominent DNA fragments revealed that these differences were due to various introns at conserved positions. The presence of introns in basidiomycetous fungi therefore has a potential use in identification of genera by analyzing PCR-generated DNA fragment patterns. Analyses of the nucleotide sequences of cloned fragments revealed variations in nucleotide sequences from 4 to 45%. By comparison of the deduced amino acid sequences, the majority of the DNA fragments were identified as members of genes for chitin synthase class II. The deduced amino acid sequences from species of the same genus differed only in one amino acid residue, whereas identity between the amino acid sequences of ascomycetous and basidiomycetous fungi within the same taxonomic class was found to be approximately 43 to 66%. Phylogenetic analysis of the amino acid sequence of class II chitin synthase-encoding gene fragments by using parsimony confirmed the current taxonomic groupings. In addition, our data revealed a fourth class of putative zymogenic chitin synthesis.

Amino Acid Sequence↗
PubMed2001

Identification and characterization of the three chitin-binding domains within the multidomain chitinase Chi92 from Aeromonas hydrophila JP101.

The gene (chi92) encoding the extracellular chitinase of Aeromonas hydrophila JP101 has been cloned and expressed in Escherichia coli. The mature form of Chi92 is an 842-amino-acid (89.830-kDa) modular enzyme comprised of a family 18 catalytic domain, an unknown-function region (the A region), and three chitin-binding domains (ChBDs; Chi92-N, ChBD(CI), and ChBD(CII)). The C-terminally repeated ChBDs, ChBD(CI) and ChBD(CII), were grouped into family V of cellulose-binding domains on the basis of sequence homology. Chitin binding and enzyme activity studies with C-terminally truncated Chi92 derivatives lacking ChBDs demonstrated that the ChBDs are responsible for its adhesion to unprocessed and colloidal chitins. Further adsorption experiments with glutathione S-transferase (GST) fusion proteins (GST-CI and GST-CICII) demonstrated that a single ChBD (ChBD(CI)) could promote efficient chitin and cellulose binding. In contrast to the two C-terminal ChBDs, the Chi92-N domain is similar to ChiN of Serratia marcescens ChiA, which has been proposed to participate in chitin binding. A truncated derivative of Chi92 that contained only a catalytic domain and Chi92-N still exhibited insoluble-chitin-binding and hydrolytic activities. Thus, it appears that Chi92 contains Chi92-N as the third ChBD in addition to two ChBDs (ChBD(CI) and ChBD(CII)).

Aeromonas hydrophila↗
PubMed2003

Growth of hyperthermophilic archaeon Pyrococcus furiosus on chitin involves two family 18 chitinases.

Pyrococcus furiosus was found to grow on chitin, adding this polysacharide to the inventory of carbohydrates utilized by this hyperthermophilic archaeon. Accordingly, two open reading frames (chiA [Pf1234] and chiB [Pf1233]) were identified in the genome of P. furiosus, which encodes chitinases with sequence similarity to proteins from the glycosyl hydrolase family 18 in less-thermophilic organisms. Both enzymes contain multiple domains that consist of at least one binding domain and one catalytic domain. ChiA (ca. 39 kDa) contains a putative signal peptide, as well as a binding domain (ChiA(BD)), that is related to binding domains associated with several previously studied bacterial chitinases. chiB, separated by 37 nucleotides from chiA and in the same orientation, encodes a polypeptide with two different proline-threonine-rich linker regions (6 and 3 kDa) flanking a chitin-binding domain (ChiB(BD) [11 kDa]), followed by a catalytic domain (ChiB(cat) [35 kDa]). No apparent signal peptide is encoded within chiB. The two chitinases share little sequence homology to each other, except in the catalytic region, where both have the catalytic glutamic acid residue that is conserved in all family 18 bacterial chitinases. The genes encoding ChiA, without its signal peptide, and ChiB were cloned and expressed in Escherichia coli. ChiA exhibited no detectable activity toward chitooligomers smaller than chitotetraose, indicating that the enzyme is an endochitinase. Kinetic studies showed that ChiB followed Michaelis-Menten kinetics toward chitotriose, although substrate inhibition was observed for larger chitooligomers. Hydrolysis patterns on chitooligosaccharides indicated that ChiB is a chitobiosidase, processively cleaving off chitobiose from the nonreducing end of chitin or other chitooligomers. Synergistic activity was noted for the two chitinases on colloidal chitin, indicating that these two enzymes work together to recruit chitin-based substrates for P. furiosus growth. This was supported by the observed growth on chitin as the sole carbohydrate source in sulfur-free media.

Amino Acid Sequence↗