scispace - formally typeset
Search or ask a question

Showing papers on "Chitin published in 1998"


Journal ArticleDOI
TL;DR: In this article, it was shown that a single amino acid substitution in the catalytic center of the 39-kDa isoform of chitotriosidase, which generates a similar sequence to that in HC gp-39, results in a loss of hydrolytic activity and creates the capacity to bind to chitin.
Abstract: In various mammals, enzymatically active and inactive members of family 18 glycosyl hydrolases, containing chitinases, have been identified. In man, chitotriosidase is the functional chitinolytic enzyme, whilst the homologous human cartilage 39-kDa glycoprotein (HC gp-39) does not exhibit chitinase activity and its function is unknown. This study establishes that HC gp-39 is a chitin-specific lectin. It is experimentally demonstrated that a single amino acid substitution in the catalytic centre of the 39-kDa isoform of chitotriosidase, which generates a similar sequence to that in HC gp-39, results in a loss of hydrolytic activity and creates the capacity to bind to chitin. The possible implication of the finding for chitinolytic and chitin-binding proteins that are produced in high quantities by activated macrophages are discussed.

357 citations


Journal ArticleDOI
Keisuke Kurita1
TL;DR: Organosoluble derivatives of chitin were prepared and used as precursors for regioselective and quantitative chemical modifications, and the effects of substituents were discussed.

353 citations


Journal ArticleDOI
TL;DR: The results suggest that different mechanisms are involved in the elicitation of POD activities by GlcNAc oligomers, and of PAL and Pod activities by partially N-acetylated chitosan polymers and that both enzymes have to be activated for lignin biosynthesis and ensuing necrosis to occur.
Abstract: Chitin, a linear polysaccharide composed of (1→4)-linked 2-acetamido-2-deoxy-β-d-glucopyranose (GlcNAc) residues, and chitosan, the fully or partially N- acetylated, water-soluble derivative of chitin composed of (1→4)-linked GlcNAc and 2-amino-2-deoxy-β-d-glucopyranose (GlcN), have been proposed as elicitors of defense reactions in higher plants. We tested and compared the ability of purified (1→4)-linked oligomers of GlcNAc (tetramer to decamer) and of GlcN (pentamer and heptamer) and partially N- acetylated chitosans with degrees of acetylation (DA) of 1%, 15%, 35%, 49%, and 60% and average degrees of polymerization between 540 and 1100 to elicit phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, lignin deposition, and microscopically and macroscopically visible necroses when injected into the intercellular spaces of healthy, nonwounded wheat ( Triticum aestivum L.) leaves. Purified oligomers of (1→4)-linked GlcN were not active as elicitors, whereas purified oligomers of (1→4)-linked GlcNAc with a degree of polymerization ≥ 7 strongly elicited POD activities but not PAL activities. Partially N- acetylated, polymeric chitosans elicited both PAL and POD activities, and maximum elicitation was observed with chitosans of intermediate DAs. All chitosans but not the chitin oligomers induced the deposition of lignin, the appearance of necrotic cells exhibiting yellow autofluorescence under ultraviolet light, and macroscopically visible necroses; those with intermediate DAs were most active. These results suggest that different mechanisms are involved in the elicitation of POD activities by GlcNAc oligomers, and of PAL and POD activities by partially N- acetylated chitosan polymers and that both enzymes have to be activated for lignin biosynthesis and ensuing necrosis to occur.

333 citations


Journal ArticleDOI
TL;DR: Chitinases catalyze the hydrolysis of chitin, an unbranched polymer of beta-1,4-N-acetylglucosamine, which plays an important physiological and ecological role in ecosystems as recyclers of chite, by generating carbon and nitrogen sources.

327 citations


Journal ArticleDOI
TL;DR: In this paper, the solubility of various derivatives of chitosan was investigated in three buffers of various pH, and some derivatives were soluble in 0.01 M phosphate buffer saline (PBS, pH = 7.2).

326 citations


Journal ArticleDOI
TL;DR: This study shows that C. violaceum produces a set of chitinolytic enzymes whose production is regulated by HHL, and finds that a pleiotropic mini-Tn5 mutant of C. Violaceum that is defective in HHL production and other quorum-sensing-regulated factors was found to be completely deficient in chitinase activity.
Abstract: Quorum sensing control mediated by N-acyl homoserine lactone (AHL) signaling molecules has been established as a key feature of the regulation of exoenzyme production in many gram-negative bacteria. In Chromobacterium violaceum ATCC 31532 a number of phenotypic characteristics, including production of the purple pigment violacein, hydrogen cyanide, antibiotics, and exoproteases are known to be regulated by the endogenous AHL N-hexanoyl-l-homoserine lactone (HHL). In this study we show that C. violaceum produces a set of chitinolytic enzymes whose production is regulated by HHL. The chitinolytic activity was induced in strains grown in the presence of chitin as the sole carbon source and quantitated in the secreted proteins by using p-nitrophenol analogs of disaccharide, trisaccharide, and tetrasaccharide oligomers of N-acetylglucosamine. By using 4-methylumbelliferyl analogs of the same oligomers of N-acetylglucosamine as substrates for proteins separated and renatured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, at least six enzymes were detected: a chitobiase with high specificity to a dimeric substrate of 87 kDa, two N-acetylglucosaminidases with apparent molecular masses of 162 and 133 kDa, two endochitinases of 108 and 67 kDa, and a chitobiosidase of 56 kDa. In addition, two unidentified bands of >205 kDa were found where a tetrameric chitin derivative was used as a substrate. A pleiotropic mini-Tn5 mutant of C. violaceum (CV026) that is defective in HHL production and other quorum-sensing-regulated factors was also found to be completely deficient in chitinolytic activity. Growth of this mutant on minimal medium with chitin supplemented with culture supernatant from the C. violaceum wild-type strain or 10 μM synthetic HHL restored chitinase production to the level shown by the parental strain. These results constitute the most complete evidence so far for regulation of chitinolytic activity by AHL signaling in a gram-negative bacterium.

264 citations


Journal ArticleDOI
01 Oct 1998-Yeast
TL;DR: The sulfuric acid method was successfully applied to determine the β‐glucan, mannan and chitin contents in cell walls of genetically well‐characterized yeast mutants defective in cell wall biosynthesis, and in Schizosaccharomyces pombe cell walls.
Abstract: A reliable acid hydrolysis method for quantitative determination of the proportion of beta-glucan, mannan and chitin in Saccharomyces cerevisiae cell wall is reported together with a simple extraction procedure to quantify within a standard error of less than 2% the proportion of the wall per gram of cell dry mass. This method is an optimized version of Saeman's procedure based on sulfuric acid hydrolysis of complex polysaccharides. It resulted in an almost complete release of glucose, mannose and glucosamine residues from cell wall polysaccharides. After complete removal of sulfate ions by precipitation with barium hydroxide, the liberated monosaccharides were separated and quantified by high performance anion-exchange chromatography with pulsed amperometric detection. The superiority of this method over the hydrolysis in either trifluoroacetic or hydrochloric acid resides in its higher efficiency regarding the release of glucose from beta 1,6-glucan and of glucosamine from chitin. The sulfuric acid method was successfully applied to determine the beta-glucan, mannan and chitin contents in cell walls of genetically well-characterized yeast mutants defective in cell wall biosynthesis, and in Schizosaccharomyces pombe cell walls. The simplicity and reliability of this procedure make it the method of choice for the characterization of cell walls from S. cerevisiae mutants generated in the EUROFAN programme, as well as for other pharmacological and biotechnological applications.

237 citations


Journal ArticleDOI
TL;DR: The results suggest that the specific interaction of these new types of chitin sulfates with gp 120 of the AIDS virus depends significantly on the sites of sulfation rather than on the total degree of substitution on sugar residues.

197 citations


Journal ArticleDOI
TL;DR: Ag-Aper1 is the first cloned PM gene from a disease vector and is likely to act as a molecular linker that connects PM chitin fibrils into a three-dimensional network.

175 citations


Journal ArticleDOI
TL;DR: Data indicate that the 10 tobacco chitinases represent complementary enzymes which may have synergistic effects on their substrates and their implication in plant defense by attacking pathogen's structural components and in plant development by maturing signal molecules is discussed.
Abstract: Ten tobacco chitinases (1,4-N-acetyl-beta-D-glucosaminide glycanhydrolase, EC 3.2.1.14) were purified from tobacco leaves hypersensitively reacting to tobacco mosaic virus. The 10 enzymes, which belong to five distinct structural classes of plant chitinases, were incubated with several potential substrates such as chitin, a beta-1,4 N-acetyl-D-glucosamine (GlcNAc) polymer, chitosan (partially deacetylated chitin), chitin oligomers of variable length and bacterial cell wall. Tobacco chitinases are all endotype enzymes that liberate oligomers from chitin and are capable of processing the chito-oligomers further at differential rates. Chitin reaction products were separated and quantified by HPLC and differential kinetics of oligomer accumulation and degradation were observed with the distinct classes of chitinases. Depending on the substrate to be hydrolysed, each isoform displayed a different spectrum of activity. For example, class I isoforms were the most active on chitin and (GlcNAc)4-6 whereas class III basic isoforms were the most efficient in inducing bacterial lysis. Class V and class VI chitinases were shown to more readily hydrolyse chitin oligomers than the chitin polymer itself. Together, these data indicate that the 10 tobacco chitinases represent complementary enzymes which may have synergistic effects on their substrates. This paper discusses their implication in plant defense by attacking pathogen's structural components and in plant development by maturing signal molecules.

154 citations


Journal ArticleDOI
TL;DR: Comparison of the amino acid sequence of the deduced polypeptide with that of other proteins showed that CBP21 is similar (45.3% amino acid identity) to CHB1 of Streptomyces olivaceoviridis, suggesting a wide distribution of this type of chitin binding protein in chitinolytic microorganisms.
Abstract: A chitin binding protein (CBP21) 21 kDa in size, is a major protein in the culture supernatant when Serratia marcescens 2170 is grown in the presence of chitin. The gene (cbp) for CBP21 was found to be located in a region 1.5 kb downstream of the chiB gene encoding chitinase B. The cbp gene encodes a polypeptide of 197 amino acids with a calculated size of 21.6 kDa containing a putative signal sequence of 27 amino acids. Comparison of the amino acid sequence of the deduced polypeptide with that of other proteins showed that CBP21 is similar (45.3% amino acid identity) to CHB1 of Streptomyces olivaceoviridis. Purified CBP21 prepared from the periplasmic fraction of Escherichia coli carrying the cloned cbp gene showed its highest binding activity to squid chitin (β-chitin) followed by colloidal chitin and regenerated chitin. Binding of CBP21 to regenerated chitin was affected by pH, in particular, low pH reduced binding activity markedly.The presence of similar chitin binding proteins in the distantly relat...

Journal ArticleDOI
TL;DR: In this article, the potential of using radiation-chemical methods for processing of cellulose and other polysaccharides in industry and agriculture has been considered, and a mechanism of the radiationchemical transformations of celluloses and other other polyscharides is suggested.
Abstract: Results of studies on the radiation-chemical transformations of cellulose, its ethers, and some other polysaccharides (xylan, starch, dextran, chitin, chitosan, and heparin) are discussed. Ionising radiation causes the degradation of these compounds accompanied by decomposition of the pyranose ring and formation of compounds with carbonyl and carboxy groups, as well as formation of hydrogen, carbon dioxide, and carbon monoxide. The efficiency of degradation increases considerably with temperature and depends on the structure of the polysaccharide and the nature of its substituents. A mechanism of the radiation-chemical transformations of cellulose and other polysaccharides is suggested. The prospects of using radiation-chemical methods for processing of cellulose and other polysaccharides in industry and agriculture are considered. The bibliography includes 213 references.

Book ChapterDOI
01 Jan 1998
TL;DR: Chitin is considered the second most plentiful organic resource on the earth next to cellulose, and is present in marine invertebrates, insects, fungi and yeasts as discussed by the authors.
Abstract: Chitin is considered the second most plentiful organic resource on the earth next to cellulose, and is present in marine invertebrates, insects, fungi and yeasts. Chitin is essentially a homopolymer of 2-acetamido-2-deoxy-β-D-glucopyranose, although some of the glucopyranose residues are in the deacetylated form as 2-amino-2-deoxy-β-D-glucopyranose. When chitin is further deacetylated to about 50% it becomes soluble in dilute acids and is referred to as chitosan. Thus chitosan is the N-deacetylated derivative of chitin, although the N-deacetylation is almost never complete. There is not a sharp boundary in the nomenclature distinguishing chitin from chitosan. Chitin does occur in nature in the fully acetylated form and has been referred to as chitan [1]. Chitosan rarely occurs in nature, but is found in the dimorphic fungus, Mucor rouxii [2]. Its occurrence in Mucor rouxii is via the enzymatic deacetylation of chitin.

Journal ArticleDOI
TL;DR: Results indicate that the chitin-binding domain helps determine the movement of chit inase along N-acetylglucosamine strands and within environments containing chitIn.
Abstract: To examine the ecology and evolution of microbial chitinases, especially the chitin-binding domain, one of the chitinase genes (chiA) from the marine bacterium Vibrio harveyi was analysed. The deduced amino acid sequence of ChiA is not very similar overall to other proteins, except for two regions, the putative catalytic and chitin-binding domains. Among all bacterial chitinases sequenced to date, there is no relationship between percentage similarity of catalytic domains and chitin-binding domains in pairwise comparisons, suggesting that these two domains have evolved separately. The chitin-binding domain appears to be evolutionarily conserved among many bacterial chitinases and is also somewhat similar to cellulose-binding domains found in microbial cellulases and xylanases. To investigate the role of the chitin-binding domain, clones producing versions of ChiA with or without this domain were examined. One version with the domain (ChiA1) bound to and hydrolysed chitin, whereas a truncated ChiA without the putative chitin-binding domain (ChiA2) did not bind to chitin but it could hydrolyse chitin, although not as well. ChiA1 diffused more slowly in agarose containing colloidal chitin than ChiA2, but diffusion of the Two proteins in agarose without colloidal chitin was similar. These results indicate that the chitin-binding domain helps determine the movement of chitinase along N-acetylglucosamine strands and within environments containing chitin.

Journal ArticleDOI
TL;DR: The stomatopod crustacean Neogonodactylus oerstedii was decayed in the laboratory under anoxic conditions and a combination of pyrolysis-gas chromatography/mass spectrometry and FTIR revealed extensive chemical changes after just 2 weeks that resulted in a cuticle composition dominated by chitin this article.

Journal ArticleDOI
TL;DR: A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution and observed values were in good agreement with those obtained by (1)H NMR and the other methods.
Abstract: A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution. The degree of acetylation was precisely evaluated on the basis of peak intensities of the characteristic products such as acetonitrile, acetic acid, and acetamide originating from the N-acetyl group of N-acetyl-d-glucosamine units of chitin/chitosan. The observed values were in good agreement with those obtained by (1)H NMR and the other methods. Moreover, the proposed technique was applicable to any kinds of chitin/chitosan samples over the whole range of acetylation including insoluble chitin/chitosan and perfectly acetylated artificial chitin having higher crystallinity to which (1)H NMR had been inapplicable.

Journal ArticleDOI
TL;DR: The phenotype of a delta chs2 null mutant suggested that CHS2 encoded the major enzyme activity in vitro and was largely responsible for elevated chitin synthase activities in microsomal preparations from hyphal cells compared to yeast cells, and CaChs3p was responsible for synthesis of most chitIn in both yeast and hyphae.
Abstract: Candida albicans has three genes encoding chitin synthase enzymes. In wild-type strains, the expression of CHS2 and CHS3 peaked 1-2 h after the induction of hyphal growth, whilst mRNA levels in a non-germinative strain, CA2, remained low under the same conditions. CHS1 gene expression did not peak during germ tube formation but remained at low levels in both yeast and hyphal growth. The pattern of gene expression did not predict the changes in measured chitin synthase activities or changes in chitin content during dimorphic transition. Chitin synthase activity increased steadily, and did not peak shortly after germ tube induction, and activity profiles were similar in germ-tube-competent and germ-tube-negative strains. The phenotype of a Δchs2 null mutant suggested that CHS2 encoded the major enzyme activity in vitro and was largely responsible for elevated chitin synthase activities in microsomal preparations from hyphal cells compared to yeast cells. However, CaChs3p was responsible for synthesis of most chitin in both yeast and hyphae. Three independent chitin assays gave markedly different estimates of the relative chitin content of yeast and hyphae and wild-type and chs mutants. Only one of the methods gave a significantly higher chitin content for hyphal compared to yeast cell walls and a lower chitin content for hyphae of the Δchs2 null mutant compared to the parental strain.

Journal ArticleDOI
TL;DR: In situ precipitation of calcium phosphate from a supersaturated solution onto chitin scaffolds can be an important route in the future production of various polymer-calcium phosphate composites.
Abstract: Composites of chitin with calcium phosphate were obtained by in situ precipitation of the mineral from a supersaturated solution onto chitin scaffolds. The chitin scaffolds were obtained by freeze drying to give a highly porous structure possessing a polar surface favorable for apatite nucleation and growth. The extent and arrangement of calcium phosphate deposits on the chitin and substituted chitin scaffolds were explored. Up to 55% by mass of calcium phosphate could be incorporated into chitin scaffolds. Deposits on the chitin surface were of a continuous apatite carpet nature while deposits on carboxymethylated chitin surfaces displayed a spherical morphology. Carboxymethylation of chitin exerts an overall inhibitory effect towards calcium phosphate deposition, but it provides for site-specific nucleation of the mineral phase. In situ precipitation can be an important route in the future production of various polymer–calcium phosphate composites. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 541–548, 1998.

Journal ArticleDOI
TL;DR: Chitin and chitosan both activated complement via the alternative pathway and activated complement components C3 and C5, but not C4, but the intensity of complement activation was greater with ch itosan than with chitin.

Journal ArticleDOI
TL;DR: Supernatants of canine polymorphonuclear cell (PMN) suspensions incubated with chitin and chitosan contained a leukotriene B4 (LTB4) concentration high enough to induce canine PMN migration in vitro, which attracted the canine PMNs in vitro.
Abstract: The effects of chitin and chitosan on the release of arachidonic acid products were investigated in this study. Supernatants of canine polymorphonuclear cell (PMN) suspensions incubated with chitin and chitosan contained a leukotriene B4 (LTB4) concentration high enough to induce canine PMN migration in vitro. The supernatants also contained the same concentration of prostaglandin E2 (PGE2) as that normally found in the peripheral blood of dogs. Intraperitoneal administration of chitosan to dogs induced peritoneal exudative fluid (PEF), but chitin did not. The PEF contained numerous PMNs and macrophages. The supernatant of PEF contained both heat-stable and heat-labile chemotactic factors for canine PMNs. It also contained enough LTB4 to attract the canine PMNs in vitro.

Journal ArticleDOI
TL;DR: The resulting branched polysaccharides showed a remarkable solubility in neutral water in sharp contrast to the insoluble linear chitin and chitosan and exhibited considerable antimicrobial activity.
Abstract: Regioselective introduction of α-mannoside branches at C-6 of chitin and chitosan has been accomplished by a series of regioselective modification reactions starting from N-phthaloyl-chitosan as a ...

Journal ArticleDOI
TL;DR: In this paper, an exo-β-d-glucosaminidase (Exoβd-N-acetylhexosamidase) was shown to be an endo-type chitosanase.
Abstract: Cellulose, chitin, and chitosan consist of β-1,4-linked glucopyranoses, and their differences are in functional groups at the C-2 positions of their constituent sugars, i.e., the hydroxyl, acetamido, and amino groups, respectively. Chitin is one of the most abundant forms of biomass next to cellulose (9). On the other hand, chitosan, a partially or fully deacetylated form of chitin, has been found only in the cell walls of limited groups of fungi in nature (2). Chitosan has had various applications, e.g., as a carrier of immobilized enzymes and a metal-removal and cohesive reagent for purification of waste streams (27). In commercial use, chitosan is obtained by chemical deacetylation of chitin. It also has biological activities. One such activity is to elicit plant defense reactions. This defense system includes formation of fungal cell wall-degrading enzymes such as endo-β-1,3-glucanase and chitinase (19) and production of phytoalexin (10). The other biological activity of chitosan is growth inhibition of bacteria and fungi (15). Chitosanases have been found in a variety of microorganisms, including bacteria and fungi (1, 6, 12, 24, 26, 30, 31). Furthermore, plant chitosanases, which also provide defensive reactions to attacks by fungal pathogens, were recently reported (5). Most purified chitosanases have been characterized as endo-type enzymes which cleave chitosans at random, and their reaction velocities are highly dependent on the degree of acetylation (D.A.) of the chitosan. On the other hand, the purification and characterization of an exo-type chitosanase called exo-β-d-glucosaminidase, which releases glucosamine (GlcN) continuously from the nonreducing end of the substrate, have so far been reported only for an actinomycete, Nocardia orientalis (21). Biological degradation of naturally occurring chitin in a partially deacetylated form is thought to be carried out by a two-step process (26). First, endo-type enzymes such as chitinase and chitosanase hydrolyze the chitinous material to oligosaccharides consisting of N-acetylglucosamine (GlcNAc) and GlcN. Second, the resulting oligomers are degraded completely to GlcNAc and GlcN by two exo-type enzymes, exo-β-d-N-acetylglucosaminidase and exo-β-d-glucosaminidase. However, the latter enzyme has not been studied at all except for that in N. orientalis. On the other hand, the former enzyme is distributed widely from animals to microorganisms, and its enzymological properties are well-characterized. The genus Trichoderma, which belongs among deuteromycetes, is known as a high-cellulase producer. Trichoderma reesei secretes at least two cellobiohydrolases (exo type; EC 3.1.2.91), four endoglucanases (EC 3.1.2.4), and two β-glucosidases (EC 3.1.2.20). These enzymes have already been purified or their genes have been cloned (22). Trichoderma harzianum is known as a mycoparasite and secretes multiple chitin-degrading enzymes, including endochitinase (EC 3.1.2.13), exochitinase, and exo-β-d-N-acetylhexosaminidase, and some of their genes have been cloned (4, 8, 11, 25). We found that T. reesei secretes multiple chitosanolytic enzymes into a culture medium under cellulase-noninducible conditions. In this paper, we describe the identification, purification, and characterization of the exo-β-d-glucosaminidase from the hyper-cellulolytic fungus T. reesei PC-3-7. We also discuss the catalytic mechanism of exo-β-d-glucosaminidase on the basis of 1H nuclear magnetic resonance (NMR) spectroscopy of the hydrolysate. To our knowledge, this is the first report on the exo-β-d-glucosaminidase from eukaryotes.

Journal ArticleDOI
TL;DR: Manipulation of the electrostatic coat of the chitin could be a method of cellular remote control for formation of the helicoid in arthropod cuticle to allow the arthropods to set up conditions that aid the self assembly process.

Journal ArticleDOI
TL;DR: It is suggested that dietary chitin, supplemented at 5%, enhances P. monodon growth, whereas chitosan depresses shrimp growth, regardless of the supplementation level.
Abstract: The effect of chitin, poly-beta-(1 --> 4)-N-acetyl-glucosamine, and chitosan, a polymer of glucosamine obtained by the deacetylation of chitin, on growth and nutrient digestibility was studied in grass shrimp, Penaeus monodon. Shrimp were fed for 8 wk diets containing no supplement (control) or 2, 5 or 10 g/100 g chitin or chitosan. Each diet was fed to triplicate groups of shrimp with a mean initial body weight of 0.45 +/- 0.05 g. Significantly higher body weight gains were observed in shrimp fed the 5% chitin diet than in those fed the 10% chitin or the control diet. The weight gain of shrimp decreased as dietary chitosan supplementation level increased (r = 0. 87, P < 0.05). Feed efficiencies (FE) and protein efficiency ratios (PER) followed the same pattern. Lower protein and lipid digestibilities and lower body protein and lipid contents were observed in shrimp fed all chitosan-containing diets than in controls (P < 0.05). Carbohydrate digestibility was lower in shrimp fed the 10% chitosan diet than in those fed the control diet. Lower protein and lipid digestibilities, body lipid content and blood cholesterol concentration were observed in shrimp fed the 10% chitin diet compared with controls (P < 0.05). Higher weight gains, body lipid contents and blood cholesterol concentrations were observed in shrimp fed the 2 and 5% chitin diets than in those fed the chitosan diets. Shrimp fed the 5% chitin diet had higher protein and lipid digestibilities and higher body protein content than those fed the 5% chitosan diet (P < 0.05). These data suggest that dietary chitin, supplemented at 5%, enhances P. monodon growth, whereas chitosan depresses shrimp growth, regardless of the supplementation level.

Journal ArticleDOI
TL;DR: Microscopical and immunological investigations revealed that CHB2 acts like a glue to mediate the contact between the fungal and the Streptomyces hyphae, and homologues of CHB1 andCHB2 are secreted by streptomycetes while growing in the presence of alpha-chitin-containing substrates.
Abstract: When co-cultivated with chitin-containing fungi, Streptomyces reticuli secretes the chitin-binding protein CHB2. Microscopical and immunological investigations revealed that CHB2 acts like a glue to mediate the contact between the fungal and the Streptomyces hyphae. CHB2 was purified to homogeneity, and the sequence of its N-terminal amino acids was determined and used to deduce an oligonucleotide, which was then used to probe a subgenomic library. The chb2 gene was cloned, sequenced and overexpressed. The deduced mature protein has a molecular mass of 18.6 kDa, and a large number of its amino acids are identical to those of CHB1 from Streptomyces olivaceoviridis. CHB2 effectively targets different types of alpha-chitin, but no other polysaccharide. The dissociation constant (Kd) for binding to purified crab shell chitin is 0.27 microM. Immunological studies suggest that homologues of CHB1 and CHB2 are secreted by streptomycetes while growing in the presence of alpha-chitin-containing substrates.

Journal ArticleDOI
TL;DR: The results suggest that the 35-kDa chitinase derives from the 52-k da chit inase by post-translational proteolytic modification.
Abstract: A chitinase gene (pCHI52) encoding the 52-kDa chitinase was isolated from a Serratia marcescens KCTC2172 cosmid library. This chitinase gene consists of 2526 bp with an open reading frame that encodes 485 amino acids. Escherichia coli harboring the pCHI52 gene secreted not only a 52-kDa but also a 35-kDa chitinase into the culture supernatant. We purified both 52-kDa and 35-kDa chitinases using a chitin affinity column and Sephacryl-S-300 gel filtration chromatography. We determined that the 17 N-terminal amino acid sequences of the 52-kDa and the 35-kDa chitinase are identical. Furthermore, a protease obtained from S. marcescens KCTC2172 cleaved the 52-kDa chitinase into the 35-kDa protein with chitinase activity. These results suggest that the 35-kDa chitinase derives from the 52-kDa chitinase by post-translational proteolytic modification. The optimal reaction temperature of 45°C and the optimal pH of 5.5 were identical for both enzymes. The specific activities of the 52-kDa and 35-kDa chitinases on natural swollen chitin were 67 μmol min−1 mg−1 and 60 μmol min−1 mg−1, respectively.

Book ChapterDOI
01 Jan 1998
TL;DR: Manifestly, such a system that is so critical a part of the insect exoskeleton, as well as being specific to arthropods among the animals, can provide a significant opportunity for the development of biologically rational pesticides.
Abstract: Chitin is a major constituent of insect cuticle that contributes to the structural integrity of the exoskeleton. It is synthesized as part of a chitin-protein complex during the molt/intermolt cycle. The current view of chitin synthesis (see review by Retnakaran and Oberlander 1993) is that oligosaccharides are transported across the cell membrane with assistance from a dolichol carrier, while assembly involves a lectin protein. Generally, 20-hydroxyecdysone (20-OHE) is needed to program chitin synthesis which commences in the epidermis after the fall in hormone titer. Manifestly, such a system that is so critical a part of the insect exoskeleton, as well as being specific to arthropods among the animals, can provide a significant opportunity for the development of biologically rational pesticides.

Journal ArticleDOI
TL;DR: A chitinolytic enzyme was purified from the culture filtrate of T. harzianum by precipitation with ammonium sulphate followed by affinity binding to swollen chitin and release with 10% (v/v) acetic acid, demonstrating that the enzyme was an exochitinase releasing N-acetylglucosamine only.

Journal ArticleDOI
TL;DR: Incubation of Aspergillus fumigatus NCPF 2140 in growth medium containing 1% chitin as sole carbon source led to induction of specific extracellular chitinolytic activity, indicating regulation by a negative feedback mechanism.
Abstract: Summary: Incubation of Aspergillus fumigatus NCPF 2140 in growth medium containing 1 % chitin as sole carbon source led to induction of specific extracellular chitinolytic activity of 1.5 μmol GlcNAc released min-1 (mg protein)-1. The effect was repressed by the inclusion of GlcNAc in the medium, indicating regulation by a negative feedback mechanism. Extracellular chitinase activity was inhibited by allosamidin (IC50 0.12 μM). Multiple chitinolytic enzymes were detected on zymograms of extracellular preparations; levels of individual enzymes induced were dependent upon whether cells were incubated with purified colloidal chitin or a crude preparation of crystalline chitin. A major, inducible, 45 kDa chitinase was purified using ammonium sulphate precipitation, chitin affinity chromatography and a novel procedure involving the electroelution of the enzyme from a substrate gel containing glycol chitin. The enzyme is a glycoprotein with endochitinase activity.

Journal ArticleDOI
TL;DR: An experiment with wood blocks indicated that chitin may be a good marker for total fungal biomass production, including living and dead mycelia, in early stages of wood decay (dry weight loss <6%).
Abstract: Cell wall chitin was determined in the mycelia of the brown rot fungus Neolentinus lepideus (Lentinus lepideus) and an isolate of the soft rot fungus Phialophora sp. to study the correlation to myc...