Showing papers on "Chitin published in 1995"
TL;DR: It is concluded that the latter polysaccharide has a central role in the organization of the yeast cell wall and the possible mechanism of synthesis and physiological significance of the cross-links is discussed.
607 citations
TL;DR: Methodology and analysis of physicochemical properties of these biopolymers are reviewed in terms of crustacean species and diverse characterization methodology, indicating the need for a more integrated approach for total resource utilization.
Abstract: Various procedures for preparation of the biopolymers chitin and chitosan have been developed over the years. Preparation methodology and analysis of physicochemical properties of these biopolymers are reviewed in terms of crustacean species and diverse characterization methodology. Such properties influence biopolymer functionality differing with crustacean species and preparation methods. Monitoring of the relationship between process conditions and chitin/chitosan products is needed to insure uniformity and proper product quality control. Research with chitosan derived from crawfish processing operations indicates the need for a more integrated approach for total resource utilization. Examples of value-added processing by-products, coupled with chitosan recovery, are noted.
425 citations
TL;DR: Experiments with appropriate mutants showed that synthesis of the chitin combined with glucan is catalyzed by chit in synthetase 3, implying that chitInase can hydrolyze the linkage between N-acetylglucosamine and glucose.
336 citations
TL;DR: Outstanding features are the materials' mechanical and chemical properties which offer numerous, largely unexplored applications in technology, chemistry, medicine, and agriculture.
Abstract: A survey on the properties of the natural nitrogen-containing polysaccharides chitin and chitosan is given Outstanding features are the materials' mechanical and chemical properties which offer numerous, largely unexplored applications in technology, chemistry, medicine, and agriculture Derivatives of chitin and chitosan are accessible by reactions of the hydroxy and amino groups with appropriate reagents Various types of gels, membranes, and fibers, including polycationic and watersoluble materials, can be formed Production of chitin and chitosan from waste crab shells involves environmentally safe processes The polysaccharides are recycled in nature by enzymatic degradation and reuse of N-acetylglucosamine for biosynthesis and catabolism Research deficits exist in economically competitive production technologies, construction of composite materials, and the ecological aspects of chemically modified chitosan
296 citations
TL;DR: Among various divalent cations Mn2+ and Hg2+ completely inhibited the purified enzyme while beta-mercaptoethanol stimulated its activity, which had potential for cell wall lysis of many fungal pathogens tested.
Abstract: Streptomyces viridificans was found to be a good chitinase producer among nine species of Streptomyces screened. Minimum levels of constitutive enzyme were observed with both simple and complex carbon substrate. Arabinose doubled the enzyme production amongst the various pentoses and hexoses used with chitin. However, with glucose end-product inhibition and catabolite repression were observed. The enzyme tolerated a wide range of temperature (30-55 degrees C) and pH (3-7.5). Among various divalent cations Mn2+ and Hg2+ completely inhibited the purified enzyme while beta-mercaptoethanol stimulated its activity. Crude and purified enzyme had potential for cell wall lysis of many fungal pathogens tested.
229 citations
TL;DR: Results suggest that Asp441, Asp562, Gln601, Arg604, and Trp605 are located in the active pocket and that they function as the catalytic residues of the enzyme.
171 citations
TL;DR: Chitin deacetylase, the enzyme that catalyzes the hydrolysis of acetamido groups of N-acetyl-D-glucosamine in chitin, has been purified to homogeneity from the culture filtrate of the fungus Colletotrichum lindemuthianum and further characterized.
156 citations
TL;DR: The enzymes from Trichoderma species that degrade fungal cell walls have been suggested to play an important role in mycoparasitic action against fungal plant pathogens and one of these enzymes was purified to homogeneity and showed an endolytic mode of action on pustulan.
Abstract: The enzymes from Trichoderma species that degrade fungal cell walls have been suggested to play an important role in mycoparasitic action against fungal plant pathogens. The mycoparasite Trichoderma harzianum produces at least two extracellular beta-1,6-glucanases, among other hydrolases, when it is grown on chitin as the sole carbon source. One of these extracellular enzymes was purified to homogeneity after adsorption to its substrate, pustulan, chromatofocusing, and, finally, gel filtration. The apparent molecular mass was 43,000, and the isoelectric point was 5.8. The first 15 amino acids from the N terminus of the purified protein have been sequenced. The enzyme was specific for beta-1,6 linkages and showed an endolytic mode of action on pustulan. Further characterization indicated that the enzyme by itself releases soluble sugars and produces hydrolytic halli on yeast cell walls. When combined with other T. harzianum cell wall-degrading enzymes such as beta-1,3-glucanases and chitinases, it hydrolyzes filamentous fungal cell walls. The enzyme acts cooperatively with the latter enzymes, inhibiting the growth of the fungi tested. Antibodies against the purified protein also indicated that the two identified beta-1,6-glucanases are not immunologically related and are probably encoded by two different genes.
150 citations
TL;DR: Despite their relatively normal growth, chitin-deficient mutants are significantly less virulent than the parental strain in both immunocompetent and immunosuppressed mice, suggesting that the reduced virulence of the mutants is not due to accelerated clearing.
Abstract: We have analyzed the role of chitin, a cell-wall polysaccharide, in the virulence of Candida albicans. Mutants with a 5-fold reduction in chitin were obtained in two ways: (i) by selecting mutants resistant to Calcofluor, a fluorescent dye that binds to chitin and inhibits growth, and (ii) by disrupting CHS3, the C. albicans homolog of CSD2/CAL1/DIT101/KT12, a Saccharomyces cerevisiae gene required for synthesis of approximately 90% of the cell-wall chitin. Chitin-deficient mutants have no obvious alterations in growth rate, sugar assimilation, chlamydospore formation, or germ-tube formation in various media. When growing vegetatively in liquid media, the mutants tend to clump and display minor changes in morphology. Staining of cells with the fluorescent dye Calcofluor indicates that CHS3 is required for synthesis of the chitin rings found on the surface of yeast cells but not formation of septa in either yeast cells or germ tubes. Despite their relatively normal growth, the mutants are significantly less virulent than the parental strain in both immunocompetent and immunosuppressed mice; at 13 days after infection, survival was 95% in immunocompetent mice that received chs3/chs3 cells and 10% in immunocompetent mice that received an equal dose of chs3/CHS3 cells. Chitin-deficient strains can colonize the organs of infected mice, suggesting that the reduced virulence of the mutants is not due to accelerated clearing.
145 citations
TL;DR: From a hydrothermal vent site off the Mexican west coast, a novel, hyperthermophilic, anaerobic archaeum was isolated, representing a new species,Thermococcus chitonophagus, using chitin, yeast extract, meat extract, and peptone for growth.
Abstract: From a hydrothermal vent site off the Mexican west coast (20°50′N, 109°06′W) at a depth of 2,600 m, a novel, hyperthermophilic, anaerobic archaeum was isolated. Cells were round to slightly irregular cocci, 1.2–2.5 μm in diameter and were motile by means of a tuft of flagella. The new isolate grew between 60 and 93°C (optimum: 85°C), from pH 3.5 to 9 (optimum: pH 6.7), and from 0.8 to 8% NaCl (optimum: 2%). The isolate was an obligate organotroph, using chitin, yeast extract, meat extract, and peptone for growth. Chitin was fermented to H2, CO2, NH3, acetate, and formate. H2S was formed in the presence of sulfur. The chitinoclastic enzyme system was oxygen-stable, cell-associated, and inducible by chitin. The cell wall was composed of a surface layer of hexameric protein complexes arranged on a p6 lattice. The core lipids consisted of glycerol diphytanyl diethers and acyclic and cyclic glycerol diphytanyl tetraethers. The G+C content was 46.5 mol%. DNA/DNA hybridization and 16S rRNA sequencing indicated that the new isolate belongs to the genusThermococcus, representing a new species,Thermococcus chitonophagus. The type strain is isoalte GC74, DSM 10152.
124 citations
TL;DR: An extracellular chitin deacetylase activity has been purified to homogeneity from autolyzed cultures of Aspergillus nidulans, an acidic glycoprotein with a pI of 2.75 and a 28% (wt/wt) carbohydrate content.
Abstract: An extracellular chitin deacetylase activity has been purified to homogeneity from autolyzed cultures of Aspergillus nidulans. This enzyme is an acidic glycoprotein with a pI of 2.75 and a 28% (wt/wt) carbohydrate content. The apparent M r of the enzyme estimated by SDS/PAGE and Superose 12 (f.p.l.c.) was around 27,000. The enzyme had an optimum pH at 7.0 and was stable in the pH range 4.0–7.5. Its optimum temperature of reaction was 50°C, and it was stable from 30° to 100°C after 1 h of preincubation. The enzyme hydrolyzed glycol chitin and oligomers of N-acetylgucosamine and to a lesser extent chitin, colloidal chitin, carboxymethylchitin, and an α-1 → 3,1 → 6-N-acetylgalactosamine-galactan among other substances with amido groups, but the enzyme did not hydrolyze peptide bonds. The role of this enzyme could be deacetylation of chitin oligosaccharides during autolysis, after action of endochitinase on cell walls.
01 Feb 1995
TL;DR: Chitosan is a polyaminosaccharide, normally obtained by alkaline deacetylation of chitin which is a very abundant naturally occurring polymeric material as discussed by the authors.
Abstract: Chitosan [(1-4) 2-amino 2-deoxy-β-D-glucan] is a polyaminosacchar-ide, normally obtained by alkaline deacetylation of chitin which is a very abundant naturally occurring polymeric material. It occurs as a principle constituent of the protective cuticles of crustacea and insects and also in the cell walls of some fungi and microorganisms.
TL;DR: Chitin deacetylase, which releases the acetyl groups of glycol chitin was purified from a fungus, Absidia coerulea, and characterized and was demonstrated to be localized near the inner face of the cell wall (periplasmic space) in the mycelia by using immunoelectron microscopy.
Abstract: Chitin deacetylase, which releases the acetyl groups of glycol chitin was purified from a fungus, Absidia coerulea, and characterized. The enzyme was purified 516-fold to homogeneity by means of 65-80% ammonium sulfate precipitation followed by chromatography on Butyl Toyoperal-650M, Gigapite (hydroxyapatite), and DEAE Toyopearl-650M. It had an apparent molecular weight of 75 kDa both on sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration chromatography, indicating that the enzyme exists as a monomer. The amino-terminal sequence was determined to be Gly-Glu-Tyr-Trp-Gln-Ser-Phe-. The enzyme is active on chitooligosaccharides with more than two N-acetylglucosamine residues (chitobiose) and is able to convert the nascent chitin synthesized by chitin synthase to chitosan in vitro. When O-hydroxyethylated chitin (glycol chitin) was used as a substrate, the optimum pH for enzyme activity was 5.0 and the optimum temperature was 50 degrees C. The enzyme was heat-stable and strongly inhibited by Fe3+. Furthermore, chitin deacetylase was demonstrated to be localized near the inner face of the cell wall (periplasmic space) in the mycelia by using immunoelectron microscopy.
TL;DR: A new assay is presented for the determination of chitin deacetylase activity employing hexa-N-acetylchitohexaose as substrate and measuring the acetate released enzymatically, as well as the pH and temperature dependence of activity and the thermostability of the enzyme.
TL;DR: Three chitinase genes (CHT1, CHT2, and CHT3) from the dimorphic human pathogen Candida albicans are cloned and all three genes show striking similarity to other chitInase genes in the literature, especially in the proposed catalytic domain.
Abstract: Chitinase (EC 3.2.1.14) is an important enzyme for the remodeling of chitin in the cell wall of fungi. We have cloned three chitinase genes (CHT1, CHT2, and CHT3) from the dimorphic human pathogen Candida albicans. CHT2 and CHT3 have been sequenced in full and their primary structures have been analyzed: CHT2 encodes a protein of 583 aa with a predicted size of 60.8 kDa; CHT3 encodes a protein of 567 aa with a predicted size of 60 kDa. All three genes show striking similarity to other chitinase genes in the literature, especially in the proposed catalytic domain. Transcription of CHT2 and CHT3 was greater when C. albicans was grown in a yeast phase as compared to a mycelial phase. A transcript of CHT1 could not be detected in either growth condition.
TL;DR: The preservation potential of chitin in the marine environment is a matter of debate as discussed by the authors, and it is shown that slightly transformed chitins represent the major component of the remaining biomass after only eight weeks.
TL;DR: Investigation ofStreptomyces olivaceoviridis as well as transformants of S. vinaceus and S. lividans carrying the exo-chiO1 gene on a multicopy vector secrete a 59-kDa chitinase which adheres strongly and under most conditions irreversibly to the substrate chit in, revealing a strong adhesion of the enzyme to its crystalline substrate via its binding domain is a prerequisite for efficient hydrolysis
Abstract: Streptomyces olivaceoviridis is an efficient chitin degrader. One of its genes encoding an exochitinase (exo-ChiO1) was previously characterized. The transcription was found to be inducible by chitin, but not by glucose. The transcriptional start site is situated 38 bp upstream of the start codon. S. olivaceoviridis as well as transformants of S. vinaceus and S. lividans carrying the exo-chiO1 gene on a multicopy vector secrete a 59-kDa chitinase which adheres strongly and under most conditions irreversibly to the substrate chitin. After having released the enzyme from the crystalline substrate in the presence of high concentrations of guanidine hydrochloride, it was purified to homogeneity by consecutive chitin- and immunoaffinity chromatographies. Immunofluorescence microscopy revealed that the enzyme specifically binds to crystalline alpha-chitin within fungi and other organisms as well as to beta-chitin, but not to colloidal chitin, chitosan, various types of cellulose, or other polysaccharides. The amino acids deduced from the highly specific binding domain (12 kDa) of this enzyme do not share significant similarity with any known region interacting with chitin or another substrate. During cultivation with chitin, the 59-kDa enzyme is proteolytically processed to a 47-kDa truncated chitinase lacking the chitin-binding domain. The 47-kDa enzyme hydrolyses crystalline chitin considerably less efficiently than the 59-kDa enzyme, whereas colloidal chitin and low-molecular-mass substrates are quite equally degraded by both enzymes at identical optimal pH (7.3) and temperature (45-55 degrees C) values. Thus a strong adhesion of the enzyme to its crystalline substrate via its binding domain is a prerequisite for efficient hydrolysis.
TL;DR: The result suggests the intriguing possibility that a bacterium-plant type of "Nod" signaling system may operate during early stages of vertebrate embryonic development and raises issues about the use of chitin synthase inhibitors as fungal-specific drugs.
Abstract: The Xenopus DG42 gene is expressed only between the late midblastula and neurulation stages of embryonic development. Recent database searches show that DG42 has striking sequence similarity to the Rhizobium NodC protein. NodC catalyzes the synthesis of chitin oligosaccharides which subsequently are transformed into bacterium-plant root signaling molecules. We find that the DG42 protein made in an in vitro coupled transcription-translation system catalyzes the synthesis of an array of chitin oligosaccharides. The result suggests the intriguing possibility that a bacterium-plant type of "Nod" signaling system may operate during early stages of vertebrate embryonic development and raises issues about the use of chitin synthase inhibitors as fungal-specific drugs.
TL;DR: It was revealed that significant quantities of N were transferred to the host in the mycorrhizal condition that led to enhanced growth rates and this was reflected in the calculation of the percentage of available substrate present in the plant.
Abstract: In acid mor-humus soils of heathland ecosystems fungi are a significant part of the soil biomass. In these organic soils chitin and hyphal wall hexosamines are major potential sources of nitrogen (N). The ability of the ericoid mycorrhizal fungus Hymenoscyphus ericae (Read) Korf & Kernan to degrade purified chitin and the hexosamines, N-acetylglucosamine, glucosamine and galactosamine when supplied as sole sources of N, was investigated in aseptic liquid culture. The fungus grew rapidly on all the organic N sources, producing the largest dry weight increase when supplied with galactosamine and similar yields on the other nitrogenous sources. Mycelial N contents of fungus grown on the hexosamines reflected the dry weight yields with the fungus grown on galactosamine having the highest N content. After 20 d only trace quantities of N-acetylglucosamine and glucosamine were present in culture filtrate, and 15% of the galactosamine remained at the final harvest. Plants of Vaccinium macrocarpon Ait. and Calluna vulgaris (L.) Hull were grown aseptically in the mycorrhizal or non-mycorrhizal condition on agar media containing chitin or a hexosamine and compared with yields and N contents in the absence of an N source. It was revealed that significant quantities of N were transferred to the host in the mycorrhizal condition that led to enhanced growth rates. The highest yields of V. macrocarpon were observed with N-acetylglucosamine, with the other hexosamines giving yields slightly below that on chitin. The yields were reflected in the calculation of the percentage of available substrate present in the plant ; up to 40% of the N-acetylglucosamine was present in the plants after 40 d.
TL;DR: Radiometrie and gel electrophoretic analyses of crude extracts and extracellular washing fluids have shown that chitin deacetylase activity massively increases when the fungus starts to penetrate through the stomata, and that formation of the enzyme is strictly differentiation-specifically controlled.
Abstract: The broad bean rust fungus Uromyces viciae-fabae exhibits chitin only on surfaces of those infection structures which in nature are formed on the plant cuticle, but not on those differentiated in the intercellular space of the host leaf. Chitin deacetylase, an enzyme which converts chitin to chitosan, has been studied during in vitro differentiation of rust infection structures. Radiometrie and gel electrophoretic analyses of crude extracts and extracellular washing fluids have shown that chitin deacetylase activity massively increases when the fungus starts to penetrate through the stomata, and that formation of the enzyme is strictly differentiation-specifically controlled. The extracellular portion of chitin deacetylase activity was about 53% in 24-h-old differentiated infection structures. Five isoforms with apparent molecular masses of 48.1, 30.7, 25.2, 15.2 and 12.7 kDa were detectable after substrate SDS-PAGE. The enzyme is temperature-sensitive and has a pH optimum of 5.5-6.0.
TL;DR: β1,4-GT has an inherent ability to utilize two different sugar nucleotides and the sugar nucleotide preference is regulatable by α-LA, which stimulates the transfer of GalNAc from UDP-GalNAc to various chitin oligomers, although the degree of stimulation decreases as the acceptor size increases.
TL;DR: A bacterial strain capable of utilizing chitosan as a sole carbon source was isolated from soil and was identified as a member of the genus Acinetobacter.
Abstract: A bacterial strain capable of utilizing chitosan as a sole carbon source was isolated from soil and was identified as a member of the genus Acinetobacter. This strain, designated CHB101, produced extracellular chitosan-degrading enzymes in the absence of chitosan. The chitosan-degrading activity in the culture fluid increased when cultures reached the early stationary phase, although the level of activity was low in the exponential growth phase. Two chitosanases, chitosanases I and II, which had molecular weights of 37,000 and 30,000, respectively, were purified from the culture fluid. Chitosanase I exhibited substrate specificity for chitosan that had a low degree of acetylation (10 to 30%), while chitosanase II degraded colloidal chitin and glycol chitin, as well as chitosan that had a degree of acetylation of 30%. Rapid decreases in the viscosities of chitosan solutions suggested that both chitosanases catalyzed an endo type of cleavage reaction; however, chitosan oligomers (molecules smaller than pentamers) were not produced after a prolonged reaction.
TL;DR: Results indicate that the enzymes cleave both the N -acetyl-β- d -glucosaminidic and the β-glucanidic linkages in partially N-acetylated chitosan molecules.
TL;DR: The relative location of crystalline alpha-chitin within various native samples of fungi and other organisms can be clearly and rapidly visualized with the help of fluorescence or confocal laser microscopy.
TL;DR: In this paper, the biodegradation of polyethylene-chitin (PE-Chitin) and polymethylene chitosan (PEChitOSan) films, containing 10% by weight chitin or chitoshan, by pure microbial cultures and in a soil environment was studied.
Abstract: The biodegradation of polyethylene-chitin (PE-chitin) and polyethylene-chitosan (PE-chitosan) films, containing 10% by weight chitin or chitosan, by pure microbial cultures and in a soil environment was studied. Three soil-inhabited organsims,Serratia marcescens, Pseudomonas aeruginosa, andBeauveria bassiana were able to utilize chitin and chitosan in prepared PE-chitin and PE-chitosan films after eight weeks of incubation at 25°C in a basal medium containing no source of carbon or nitrogen. In a soil environment, the biodegradation of those films was studied and compared with a commercial biodegradable film containing 6% by the weight of corn starch. In soil placed in the lab, 73.4% of the chitosan and 84.7% of the chitin in the films were degraded, while 46.5% of the starch in the commercial film was degraded after six months of incubation. In an open field, 100% of the chitin and 100% of the chitosan in the films were degraded, but only 85% of the starch in the commercial film was degraded after six months of incubation. The weight of controls, (polyethylene films), remained mainly stable during the incubation period. Both PE-chitin and PE-chitosan films degraded at a higher rate than the commercial starch-based film in a soil environment indicating the potential use of chitin-based films for the manufacturing of biodegradable packaging materials.
TL;DR: From the results of the toxicity assay using mouse fibroblast cells, beta-chitin sensor, constructed with chitin, glucose oxidase and gold electrode, showed no particular toxicity.
TL;DR: Suspension-cultured Wasabia japonica cells derived from mesophyll protoplast secreted abundant basic chitinases into the medium and both showed lysozyme activity when Micrococcus lysodeikiticus was used as the substrate.
TL;DR: It is concluded that the cup is the site of assembly of R. pachyptila's giant β chitin microfibrils, and the in vitro secretory activity is an indication of good physiological state of the repressurized animals, despite the drastic environmental changes that occur during collection.
Patent•
30 May 1995
TL;DR: In this paper, a method for controlling plant diseases caused by the fungi Botrytis cinerea and Alternaria alternata, by applying to a growing plant or to fruit or vegetables before or after harvesting, is described.
Abstract: The invention relates to a method for controlling plant diseases caused by the fungi Botrytis cinerea and Alternaria alternata, by applying to a growing plant or to fruit or vegetables before or after harvesting, a composition which comprises an effective amount for controlling said fungi of at least one oligosaccharide ingredient, active against Botrytis cinerea and Alternaria alternata, and selected from oligosaccharides obtainable by hydrolysis of chitin, β-glucan and other similarly active polysaccharides, excluding chitosan, of cell walls of fungi, yeasts, marine plants and exoskeletons of arthropods, The composition also forms part of the invention, as does an analogous method and composition for a method for controlling plant diseases caused by Botrytis cinerea, and utilizing at least one oligosaccharide ingredient, active against Botrytis cinerea selected from oligosaccharides obtainable by hydrolysis of chitosan, and having a molecular weight within the range of about 500 to about 10,000 daltons, provided that in this instance the composition excludes acetic acid.
TL;DR: Results show that cells that have been subjected to hypoosmotic stress have raised native chit in synthase activities, and it is suggested that stressing the membrane may cause a conformational change in chitin synthase molecules in the membrane or changes in the interactions with the wall.
Abstract: Apical hyphal extension involves very localized apical deposition of newly synthesized wall skeletal material, notably chitin. A branch forms where a new localized site of chitin deposition occurs ...