Showing papers on "Chitin published in 1992"
TL;DR: Ac-AMP1 and Ac-AMP2 inhibit the growth of different plant pathogenic fungi at much lower doses than other known antifungal chitin-binding proteins and show some activity on Gram-positive bacteria.
Abstract: Two antimicrobial peptides (Ac-AMP1 and Ac-AMP2) were isolated from seeds of amaranth (Amaranthus caudatus), and their physicochemical and biological properties were characterized. On the basis of fast atom bombardment mass spectroscopy, Ac-AMP1 and Ac-AMP2 have monoisotopic molecular masses of 3025 and 3181, respectively. Both proteins have pI values above 10. The amino acid sequence of Ac-AMP1 (29 residues) is identical to that of Ac-AMP2 (30 residues), except that the latter has 1 additional residue at the carboxyl terminus. The sequences are highly homologous to the cysteine/glycine-rich domain occurring in many chitin-binding proteins. Both Ac-AMP1 and Ac-AMP2 bind to chitin in a reversible way. Ac-AMP1 and Ac-AMP2 inhibit the growth of different plant pathogenic fungi at much lower doses than other known antifungal chitin-binding proteins. In addition, they show some activity on Gram-positive bacteria. The antimicrobial effect of Ac-AMP1 and Ac-AMP2 is strongly antagonized by cations.
316 citations
TL;DR: The ultrastructural study showed that chitosan caused deep erosion of the cell wall as well as increasing the cell-wall thickness, and this may well upset the balance between biosynthesis turnover of chitin, thereby rendering the cell walls more viscoelastic.
293 citations
TL;DR: Chitosan is a cationic polyelectrolyte obtained after N-deacetylation of chitin by alkaline treatment as mentioned in this paper, and the adsorption and interaction between chitosin layers have been investigated.
Abstract: Chitosan is a cationic polyelectrolyte obtained after N-deacetylation of chitin by alkaline treatment. The adsorption of chitosan and the interaction between chitosan layers have been investigated ...
276 citations
TL;DR: Three proteins which display chitinase activity were purified from the supernatants of Trichoderma harzianum CECT 2413 grown in minimal medium supplemented with Chitin as the sole carbon source, suggesting that each protein is encoded by a different gene.
Abstract: Three proteins which display chitinase activity were purified from the supernatants of Trichoderma harzianum CECT 2413 grown in minimal medium supplemented with chitin as the sole carbon source. Purification was carried out after protein precipitation with ammonium sulphate, adsorption to colloidal chitin and digestion, and, finally, chromatofocusing. By this procedure, two chitinases of 42 kDa (CHIT42) and 37 kDa (CHIT37) were purified to homogeneity, as judged by SDS/PAGE and gel filtration, whereas a third, of 33 kDa (CHIT33), was highly purified. The isoelectric points for CHIT42, CHIT37 and CHIT33 were 6.2, 4.6 and 7.8, respectively. The three enzymes displayed endochitinase activities and showed different kinetic properties. CHIT33 was able to hydrolyze chitin oligomers of a polymerization degree higher than n= 4, its Km for colloidal chitin being 0.3 mg/ml. CHIT42 and CHIT37 were able to hydrolyze chitin oligomers with a minimal polymerization degree of n= 3, their Km values for colloidal chitin being 1.0 mg/ml and 0.5 mg/ml respectively. With regard to their lytic activity with purified cell walls of the phytopathogenic fungus Botrytis cinerea, a hydrolytic action was observed only when CHIT42 was present. Antibodies against CHIT42 and CHIT37 specifically recognized the proteins and did not display cross-reaction, suggesting that each protein is encoded by a different gene.
265 citations
TL;DR: Fragments homologous to chitin synthase were amplified from the genomic DNA of 14 fungal species and deduced amino acid sequences fell into three distinct classes, which could represent separate functional groups.
Abstract: Comparison of the chitin synthase genes of Saccharomyces cerevisiae CHS1 and CHS2 with the Candida albicans CHS1 gene (UDP-N-acetyl-D-glucosamine:chitin 4-beta-N-acetylglucosaminyltransferase, EC 2.4.1.16) revealed two small regions of complete amino acid sequence conservation that were used to design PCR primers. Fragments homologous to chitin synthase (approximately 600 base pairs) were amplified from the genomic DNA of 14 fungal species. These fragments were sequenced, and their deduced amino acid sequences were aligned. With the exception of S. cerevisiae CHS1, the sequences fell into three distinct classes, which could represent separate functional groups. Within each class phylogenetic analysis was performed. Although not the major purpose of the investigation, this analysis tends to confirm some relationships consistent with current taxonomic groupings.
246 citations
TL;DR: The application of wheat germ agglutinin, a lectin with N-acetylglucosamine-binding specificity, in conjunction with gold-complexed ovomucoid, to tissue sections showed that the walls of severely altered hyphal cells were labelled except in the area closely appressed to host cell walls, suggesting that extracellular chitinases accumulate in the host's cell walls but are not the primary determinants of fungal damage.
191 citations
TL;DR: Using a novel screen, it is identified three mutations, designated csd2, csd3, and csd4, that reduce levels of chitin in vivo by as much as 10-fold without causing any obvious perturbation of cell division.
Abstract: In Saccharomyces cerevisiae, chitin forms the primary division septum and the bud scar in the walls of vegetative cells. Three chitin synthetic activities have been detected. Two of them, chitin synthase I and chitin synthase II, are not required for synthesis of most of the chitin present in vivo. Using a novel screen, I have identified three mutations, designated csd2, csd3, and csd4, that reduce levels of chitin in vivo by as much as 10-fold without causing any obvious perturbation of cell division. The csd2 and csd4 mutants lack chitin synthase III activity in vitro, while csd3 mutants have wild-type levels of this enzyme. In certain genetic backgrounds, these mutations cause temperature-sensitive growth on rich medium; inclusion of salts or sorbitol bypasses this phenotype. Gene disruption experiments show that CSD2 is nonessential; a small amount of chitin, about 5% of the wild-type level, is detected in the disruptants. DNA sequencing indicates that the CSD2 protein has limited, but statistically significant, similarity to chitin synthase I and chitin synthase II. Other significant similarities are to two developmental proteins: the nodC protein from Rhizobium species and the DG42 protein of Xenopus laevis. The relationship between the nodC and CSD2 proteins suggests that nodC may encode an N-acetylglucosaminyltransferase that synthesizes the oligosaccharide backbone of the nodulation factor NodRm-1.
176 citations
TL;DR: It is proposed that soluble chitin fragments released from fungal cell walls through the action of constitutive rice chit inases serve as biotic elicitors of defense-related responses in rice.
Abstract: Cell-free extracts of UV-irradiated rice (Oryza sativa L.) leaves have a much greater capacity for the synthesis from geranylgeranyl pyrophosphate of diterpene hydrocarbons, including the putative precursors of rice phytoalexins, than extracts of unstressed leaves (KA Wickham, CA West [1992] Arch Biochem Biophys 293: 320-332). An elicitor bioassay was developed on the basis of these observations in which 6-day-old rice cell suspension cultures were incubated for 40 hours with the substance to be tested, and an enzyme extract of the treated cells was assayed for its diterpene hydrocarbon synthesis activity as a measure of the response to elicitor. Four types of cell wall polysaccharides and oligosaccharide fragments that have elicitor activity for other plants were tested. Of these, polymeric chitin was the most active; a suspension concentration of approximately 7 micrograms per milliliter gave 50% of the maximum response in the bioassay. Chitosan and a branched β-1,3-glucan fraction from Phytophthora megasperma f. sp. glycinea cell walls were only weakly active, and a mixture of oligogalacturonides was only slightly active. A crude mycelial cell wall preparation from the rice pathogen, Fusarium moniliforme, gave a response comparable to that of chitin, and this activity was sensitive to predigestion of the cell wall material with chitinase before the elicitor assay. N-Acetylglucosamine, chitobiose, chitotriose, and chitotetrose were inactive as elicitors, whereas a mixture of chitin fragments solubilized from insoluble chitin by partial acid hydrolysis was highly active. Constitutive chitinase activity was detected in the culture filtrate and enzyme extract of cells from a 6-day-old rice cell culture; the amount of chitinase activity increased markedly in both the culture filtrate and cell extracts after treatment of the culture with chitin. We propose on the basis of these results that soluble chitin fragments released from fungal cell walls through the action of constitutive rice chitinases serve as biotic elicitors of defense-related responses in rice.
152 citations
TL;DR: The results indicate that, in addition to chitinase, lysis requires other gene products that may become limiting, such as demethylallosamidin, a much better protector against lysis.
Abstract: Summary: Previous results [E. Cabib, A. Sburlati, B. Bowers & S. J. Silverman (1989) Journal of Cell Biology 108, 1665-1672] strongly suggested that the lysis observed in daughter cells of Saccharomyces cerevisiae defective in chitin synthase 1 (Chs1) was caused by a chitinase that partially degrades the chitin septum in the process of cell separation. Consequently, it was proposed that in wild-type cells, Chs1 acts as a repair enzyme by replenishing chitin during cytokinesis. The chitinase requirement for lysis has been confirmed in two different ways: (a) demethylallosamidin, a more powerful chitinase inhibitor than the previously used allosamidin, is also a much better protector against lysis and (b) disruption of the chitinase gene in chs1 cells eliminates lysis. Reintroduction of a normal chitinase gene, by transformation of those cells with a suitable plasmid, restores lysis. The percentage of lysed cells in strains lacking Chs1 was not increased by elevating the chitinase level with high-copy-number plasmids carrying the hydrolase gene. Furthermore, the degree of lysis varied in different chs1 strains; lysis was abolished in chs1 mutants containing the scs1 suppressor. These results indicate that, in addition to chitinase, lysis requires other gene products that may become limiting.
138 citations
01 Jan 1992
TL;DR: A critical evaluation of a number of potential sources of chitin has been given by Allan et al. as discussed by the authors, who estimated the total annually accessible chitins from krill, 39 × 103 t from shellfish (crab, shrimp, prawn, lobster and crayfish), 32 × 103 T from fungi, 22 × 103 TT from clams and oysters and 1 × 103 TF from squid.
Abstract: Despite the great natural abundance of chitin, much of the annual produc tion is not readily accessible for utilisation as a raw material. In this it differs markedly from cellulose. A critical evaluation of a number of potential sources of chitin has been given by Allan et al.1 Their global estimate of the total annually accessible chitin was 150 × 103 t, of which 56 × 103 t was from krill, 39 × 103 t from shellfish (crab, shrimp, prawn, lobster and crayfish), 32 × 103 t from fungi, 22 × 103 t from clams and oysters and 1 × 103 t from squid. This total is much less than the estimated total of chitin produced annually by biosynthesis — one species alone, the marine copepods, is estimated to produce 109 t of chitin annually2 — and a number of factors limiting the extent to which different sources may be utilised were discussed.1
133 citations
TL;DR: No significant differences in DIT101 transcript levels could be detected indicating absence of sporulation‐specific transcriptional regulation, but the amount of DIT 101 transcript changed significantly at different stages of the mitotic cell cycle, peaking after septum formation, but before cytokinesis.
Abstract: A mutant screen has been designed to isolate mutants in Saccharomyces cerevisiae deficient in spore wall dityrosine. As shown by electron microscopy, most of the mutant spores lacked only the outermost, dityrosine-rich layer of the spore wall. Mutant dit101, however, was additionally lacking the chitosan layer of the spore wall. Chemical measurements showed that this mutant does not synthesize chitosan during sporulation. The mutant spores were viable but sensitive to lytic enzymes (glusulase or zymolyase). Unlike most of the dit-mutants, dit101 did show a distinctive phenotype in vegetative cells: they grew normally but contained very little chitin and were therefore resistant to the toxic chitin-binding dye, Calcofluor White. The cells showed barely detectable staining of the walls with Calcofluor White or primulin. The decrease in the amount of chitin in vegetative cells and the absence of chitosan in spores suggested that the mutant dit101 could be defective in a chitin synthase. Indeed, a genomic yeast clone harboring the gene, CSD2, sharing significant sequence similarity with yeast chitin synthases I and II (C. E. Bulawa (1992), Mol. Cell. Biol. 12, 1764-1776), complemented our mutant and was shown to correspond to the chromosomal locus of dit101. Thus, the mutations dit101 and csd2 (and probably also call; M. H. Valdivieso et al., (1991), J. Cell Biol. 114, 101-109) were shown to be allelic. The gene was mapped to chromosome II and was located about 3 kb distal of GAL1. Using this DNA clone, a transcript of about 3500-4000 nucleotides was detected. Comparing RNA isolated from vegetative cells and from sporulating cells at different times throughout the sporulation process, no significant differences in DIT101 transcript levels could be detected indicating absence of sporulation-specific transcriptional regulation. However, the amount of DIT101 transcript changed significantly at different stages of the mitotic cell cycle, peaking after septum formation, but before cytokinesis. As most of the chitin synthesis of vegetative cells occurs at this stage of the cell division cycle, chitin synthesis mediated by DIT101 could be primarily regulated at the level of transcription in vegetatively growing cells.
TL;DR: Of the culture parameters studied, length of incubation and medium composition effected biomass production and molecular weight, and modification of the processing protocol, including the type and strength of acid, and cell wall disruption in acid prior to refluxing were used to optimize the efficiency of chitosan extraction.
Abstract: The isolation of chitosan from a fungal source offers the potential of a product with controlled physicochemical properties not obtainable by the commercial chemical conversion of crustacean chitin. A variety of culture and processing protocols using Mucor rouxii were studied for their effects on biomass yield and chitosan molecular weight. Weight-averaged molecular weight determined by gel permeation chromotography ranged from 2.0 x 10(5) to approximately 1.4 x 10(6) daltons. The chitosan yield ranged from 5% to 10% of total biomass dry weight and from 30% to 40% of the cell wall. Of the culture parameters studied, length of incubation and medium composition effected biomass production and molecular weight. Modification of the processing protocol, including the type and strength of acid, and cell wall disruption in acid prior to refluxing were used to optimize the efficiency of chitosan extraction.The degree of deacetylation of fungal and commercial chitosans was compared using infrared spectrometry, titration, and first derivative of UV absorbance spectrometry. The chitosan obtained directly from the fungal cell wall had a higher degree of deacetylation than commercial chitosan from the chemical conversion process.
TL;DR: Chitinase (EC 3.2.1.14), from the culture filtrate of Trichoderma harzianum, was successively purified by precipitation with ammonium sulfate followed by ion-exchange chromatography on Q-Sepharose, gel filtration on Sephadex G-100, and hydrophobic interaction on Phenyl- Sepharose CL-4B.
TL;DR: Inhibition has only been observed of spore germination, of cell separation in budding yeasts and of the action of a yeast toxin, and not of apical extension or branching, but the finding that chitinase activities in situ have different properties to those in cell homogenates, and appear to be protected from environmental stresses is explained.
Abstract: Filamentous fungi with chitin as a major component of their cell walls produce chitinases at all stages of active growth, i.e. during spore germination, exponential growth and mycelial development. The roles of chitinases in these processes have been investigated by assessing the effects of treatment with the inhibitor, allosamidin. Inhibition has only been observed, however, of spore germination, of cell separation in budding yeasts and of the action of a yeast toxin, and not of apical extension or branching. This may be explained by the finding that chitinase activities in situ have different properties to those in cell homogenates, and appear to be protected from environmental stresses.
01 Jan 1992
TL;DR: Chitin is one of the most abundant organic materials, being second only to cellulose in the amount produced annually by biosynthesis as mentioned in this paper, and occurs in animals, particularly in crustacea, molluscs and insects where it is an important constituent of the exoskeleton.
Abstract: Chitin is one of the most abundant organic materials, being second only to cellulose in the amount produced annually by biosynthesis.1 It occurs in animals, particularly in crustacea, molluscs and insects where it is an important constituent of the exoskeleton, and in certain fungi where it is the principal fibrillar polymer in the cell wall. Its occurrence has been reviewed by Jeuniaux2 and by Richards3 and a table of the distribution of chitin in living organisms, adapted from that given by Jeuniaux,4 is given in Table 1.1.
TL;DR: It is suggested that the growth inhibition of Trichoderma by hydrolytic enzymes is the consequence of a thinning of the cell wall in the hyphal apex, leading to an imbalance of turgor pressure and wall tension which causes the tip to swell and to burst.
Abstract: Plant chitinases and β-1,3-glucanases have been demonstrated to inhibit fungal growth in model experiments, both on agar plates or in liquid media. Here,Trichoderma longibrachiatum was taken as a model to study the morphological changes caused by chitinase and glucanase treatments, using cytochemical techniques in combination with fluorescence and electron microscopy. Chitinase, alone or in the presence of glucanase, arrested growth of the hypha: it affected the extreme tip of the fungus producing a thinning of the wall, a balloon-like swelling and a rupture of the plasma membrane. Chitin and glucans were present in the wall, as shown by lectinand enzyme-binding experiments, but they had a different susceptibility to chitinase and β-1,3-glucanase. Chitin was present at the apex and in the inner parts of the lateral walls; it was more susceptible to chitinase at the tip than in the subapical part. Glucans mostly occurred on the outer layer where they were degraded by glucanase. The latter did not affect the inner hyphal skeleton. It is suggested that the growth inhibition ofTrichoderma by hydrolytic enzymes is the consequence of a thinning of the cell wall in the hyphal apex, leading to an imbalance of turgor pressure and wall tension which causes the tip to swell and to burst.
TL;DR: Northern blot analysis shows that strikingly different levels of synthase 1 and 2 expression occur during yeast and hyphal phases of Candida growth.
Abstract: Summary
Chitin, the β1,4-linked polymer of N-acetylglucosamine, is a fibrous polysaccharide that in many yeasts helps to maintain the structure of the mother-bud junction and in filamentous fungi is often the major supporting component of the cell wall. We have previously described a Candida albicans chitin synthase, CHS1. The DNA and derived protein sequences of a second gene, CHS2, are presented and compared with previously published gene sequences. Northern blot analysis shows that strikingly different levels of synthase 1 and 2 expression occur during yeast and hyphal phases of Candida growth.
TL;DR: Three barley proteins were found to inhibit growth of Trichoderma harzianum in microtiter plate assays using ∼‐10 μg/ml concentrations and in lower concentrations in a synergistic way when mixed either with barley chitinase C (a PR‐3 type protein) or with barley protein R ( a PR‐5 type protein).
TL;DR: A highly efficient chitosanase producer, the actinomycete N174, identified by chemotaxonomic methods as belonging to the genus Streptomyces was isolated from soil and showed an endo-splitting type of activity and the end-product of chitOSan degradation contained a mixture of dimers and trimers of d-glucosamine.
Abstract: A highly efficient chitosanase producer, the actinomycete N174, identified by chemotaxonomic methods as belonging to the genus Streptomyces was isolated from soil. Chitosanase production by N174 was inducible by chitosan or d-glucosamine. In culture filtrates the chitosanase accounted for 50–60% of total extracellular proteins. The chitosanase was purified by polyacrylic acid precipitation, CM-Sepharose and gel permeation chromatography. The maximum velocity of chitosan degradation was obtained at 65° C when the pH was maintained at 5.5. The enzyme degraded chitosans with a range of acetylation degrees from 1 to 60% but not chitin or CM-cellulose. The enzyme showed an endo-splitting type of activity and the end-product of chitosan degradation contained a mixture of dimers and trimers of d-glucosamine.
TL;DR: Results indicate that both chitin and beta-1,3-glucan are likely to contribute to the structural rigidity of the cell wall.
Abstract: By screening for the osmotically remediable phenotype, mutations in two genes (orlA and orlB) affecting the cell wall chitin content of Aspergillus nidulans were identified. Strains carrying temperature-sensitive alleles of these genes produce conidia which swell excessively and lyse when germinated at restrictive temperatures. Growth under these conditions is remedied by osmotic stabilizers and by N-acetylglucosamine (GlcNAc). Remediation by GlcNAc suggests that the mutations affect early steps in the synthesis of chitin. Temperature and medium shift experiments indicate that the phenotype is the result of decreased synthesis rather than increased chitin degradation and that osmotic stabilizers act to stabilize a defective wall rather than to stabilize the gene product. Two genes, orlC and orlD, which affect cell wall beta-1,3-glucan content were also identified. Walls from strains carrying mutations in these genes exhibit normal amounts of alpha-1,3-glucan and chitin but reduced amounts of beta-1,3-glucan. As for the chitin-deficient mutants, orlC and orlD mutants spontaneously lyse on conventional media but are remedied by osmotic stabilizers. These results indicate that both chitin and beta-1,3-glucan are likely to contribute to the structural rigidity of the cell wall. Images
01 Jan 1992
01 Jan 1992
TL;DR: Chitin is a relatively intractable polymer and despite its structural similarity to cellulose it is insoluble in typical cellulose solvents such as cuprammonium hydroxide (Schweizer's reagent), cupriethylene diamine and Cadoxen as mentioned in this paper.
Abstract: Chitin is a relatively intractable polymer and despite its structural similarity to cellulose it is insoluble in typical cellulose solvents such as cuprammonium hydroxide (Schweizer’s reagent), cupriethylene diamine and Cadoxen. However there are a limited number of solvent systems which may be grouped together in three classes.
TL;DR: The presence of chitin in hyphal cell walls and regenerating protoplast walls of Saprolegnia monoi¨ca was demonstrated by biochemical and biophysical analyses.
TL;DR: An N-acetyl-D-[14C]glucosamine radiolabel incorporation assay has been used to monitor chitin biosynthesis in whole cells of Candida albicans both in vitro and in vivo in two different mouse infection models, one using the peritoneal cavity as a chamber in which to add and retrieve cells and the other using infected kidneys.
Abstract: An N-acetyl-D-[14C]glucosamine radiolabel incorporation assay has been used to monitor chitin biosynthesis in whole cells of Candida albicans both in vitro and in vivo in two different mouse infection models, one using the peritoneal cavity as a chamber in which to add and retrieve cells and the other using infected kidneys. Specific labeling of chitin in alkali-insoluble material was confirmed by chitinase digestion, analysis of acid hydrolysates, and the use of nikkomycin Z as a probe. Nikkomycin Z was shown to strongly inhibit chitin biosynthesis in C. albicans grown in vitro and in vivo in both models. This demonstrates that nikkomycin Z-susceptible chitin synthase activity is present in C. albicans when the fungus is in its pathogenic state in vivo. The limited use of nikkomycin as a therapeutic agent is discussed.
TL;DR: Overall, it is shown that seabirds have a capacity to assimilate a considerable portion of the carbon and nitrogen present as chitin in the exoskeleton of their prey, but it is not demonstrated that assimilation actually occurs.
Abstract: ABSTRAC.-AS a structural component of crustacean exoskeletons, chitin is the most important carbohydrate in the diets of many marine carnivores. To investigate the physiological and biochemical adaptations that may enable seabirds to break down this "prey defense," we estimated chitin digestibilities for Sooty Albatrosses (Phoebetria fusca), White-chinned Petrels (Procellaria aequinoctialis), Rockhopper Penguins (Eudyptes chrysocome), Gentoo Penguins (Pygoscelis papua), King Penguins (Aptenodytes patagonicus) and Leach's Storm-Petrels (Oceanodroma leucorhoa) fed Antarctic krill (Euphausia superba). These species retain a substantial proportion (46.5 ? SD of 13.1%, 39.1 ? 4.9%, 52.8 ? 37.6%, 45.3 ? 5.6%, 84.8 ? 11.7% and 35 ? 12.2%, respectively) of ingested chitin. We also obtained preliminary estimates of chitinolytic activity in the gastric mucosae of the above six species by incubating extracts of tissue samples with a chitin substrate and measuring the production of the end product of chitin hydrolysis, N-acetyl-D-glucosamine (NAG). Chitinolytic activity (up to 5,000 ,ug NAG h-l g-1 expressed per gram tissue) was measured from proventricular tissue and within the activity range (1,350 to 61,650 ytg NAG h-l g-1) reported for eight other avian species. In order to assess the energetic and nutritional benefits of chitinolytic activity in seabirds, we studied gastrointestinal absorption of the end products of chitinolysis in Leach's StormPetrels. The overall absorption efficiency of NAG and its deacetylated precursor, glucosamine (Gln), in this species was 44.0 ? 3.0% and 11.0 ? 1.9%, respectively. These absorption efficiencies were significantly less than for glucose, which was absorbed with an efficiency of 90.6 ? 2.5%. No absorption of NAG and Gln occurred in the proventriculus. Overall, we showed that seabirds have a capacity to assimilate a considerable portion of the carbon and nitrogen present as chitin in the exoskeleton of their prey, but we have not demonstrated that assimilation actually occurs. The potential costs and benefits of chitin hydrolysis, as well as the absorption of the breakdown products, need to be assessed. Received 24 May 1991, accepted 18 December 1991.
TL;DR: It is proposed that amino sugar (and chitin biosynthesis) is partially regulated by phosphorylation-dephosphorylation of the amidotransferase or a protein regulator of the enzyme.
Abstract: Strains of Aspergillus nidulans carrying the orlA1 or tse6 allele are deficient in cell wall chitin and undergo lysis at restrictive temperatures. The strains are remediable by osmotic stabilizers or by the presence of N-acetylglucosamine (GlcNAc) in the medium. The remediation by GlcNAc suggests that the lesion(s) in chitin synthesis resides in the amino sugar biosynthetic pathway prior to the synthesis of N-acetylglucosamine-6-phosphate. orlA1 strains grown at permissive temperature exhibit an abnormally low specific activity for L-glutamine:fructose-6-phosphate amidotransferase (EC 2.6.1.16, amidotransferase), the first enzyme unique to amino sugar synthesis. In addition, the enzyme produced is temperature sensitive in vitro. tsE6 strains grown at permissive temperature show virtually no amidotransferase activity. This finding is consistent with an extremely labile enzyme which is destroyed by cell breakage and extract preparation. The enzyme must be active in vivo at permissive temperatures since GlcNAc is not required for growth. Thus, two structural genes (orlA and tsE) are necessary for the amidotransferase activity. bimG11 strains are temperature sensitive for a type 1 protein phosphatase involved in cell cycle regulation and arrest in mitosis. Like orlA1 and tsE6 strains, conidia from bimG11 strains swell excessively when germinated and lyse; the germlings produced are deficient in chitin content. The amidotransferase from wild-type and mutant strains is sensitive to feedback inhibition by uridine diphosphate-N-acetylglucosamine. The sensitivity of the amidotransferase from bimG11 strains is dependent on growth temperature, while that from wild-type strains is independent of temperature. The enzyme can be desensitized in vitro under conditions consistent with a protein phosphatase reaction. It is proposed that amino sugar (and chitin biosynthesis) is partially regulated by phosphorylation-dephosphorylation of the amidotransferase or a protein regulator of the enzyme.
TL;DR: It is suggested that the plant cells response to various elicitors, and then produce different chitinase isozymes in a specific induction pattern, as the concentration of the elicitor increased, the induction time was shorter.
Abstract: Chitinase involved in plant self-defense was investigated by inoculation of yam (Dioscorea opposita Thunb) callus with autoclaved mycelia of Fusarium oxysporum Schl. f. sp. raphani Kend. et Snyd., ethylene, and chitin and chitosan oligosaccharides. The induction of chitinase was followed by measuring the enzyme activity, and the isozyme pattern was also analyzed by activity staining and immunoblotting after disc- and SDS-PAGE. Autoclaved Fusarium oxysporum induced acidic chitinases named El and E3 with MW 33, 500 in the callus, while ethylene and oligosaccharides of chitin and chitosan induced some chitinases more basic than E1 and E3, in addition to E1 and E3. These included large chitinases with MW 38, 000 and immunologically different chitinases from E1 and E3. In total, nine chitinases were induced. Isozyme patterns of chitinase induced were different among the elicitors used, although E1 and E3 were commonly induced in all cases. Oligosaccharides of chitin and chitosan showed different chain-length d...