Showing papers on "Chitinase published in 1979"

Evidence for Covalent Linkages between Chitin and β-Glucan in a Fungal Wall

Abstract: SUMMARY: Covalent linkages between chitin and β-glucan in the wall of Schizophyllum commune were indicated by the markedly changed solubility characteristics of the glucan when chitin was specifically removed either (i) by enzymic digestion with purified chitinase or (ii) by first deacetylating the chitin with alkali followed by depolymerization of the deacetylated chitin with nitrous acid. After depolymerization of the chitin, two types of β-glucans could be isolated: one was water-soluble and highly branched, the other was alkali-soluble with branches only one glucose unit long. Lysine (50%) and citrulline (20%) were the major amino acids in the R-glucan/chitin complex. By digesting 90% of the β-glucan in the R-glucan/chitin complex with (1→3)-β-glucanase, a residue was obtained which, on hydrolysis with chitinase, yielded N-acetylglucosamine and a compound containing (N-acetyl)-glucosamine, lysine and/or citrulline. A model is proposed for the R-glucan/chitin complex in which amino acids, especially lysine and citrulline, are involved in the linkages between glucan and chitin.

Chitinolytic enzymes in the digestive system of marine fishes

Abstract: Chitinase, exo-N-acetyl-β-D-glycosaminidase (NAGase) and lysozyme activities were assayed in the digestive tract of 6 species of marine fishes: Myxine glutinosa (cyclostome), Chimaera monstrosa (holocephalan), Squalus acanthias, Etmopterus spinax, Raja radiata (elasmobranchs) and Coryphaenoides rupestris (teleost). Strong chitinase activity was found in the gastric mucosa of the elasmobranchs (S. acanthias, E. spinax and R. radiata) and the teleost (Coryphaenoides rupestris). A remarkably high chitinase activity occurred in the pancreas of the stomachless holocephalan fish Chimaera monstrosa. NAGase activity was strong in the digestive tract of all species. It could be concluded that marine fishes with diets consisting largely of chitinous invertebrates may display high chitinase and NAGase activities in their digestive system; however, only low chitinase activity was found in the intestine of the cyclostome Myxine glutinosa. Coryphaenoides rupestris gastric mucosa chitinase had one optimum activity at pH 1.25, whereas S. acanthias chitinase had two optima, at pH 1.6 and 3.6. The NAGase pH-activity curves from S. acanthias and R. radiata gastric mucosa displayed similar optima, at pH 4.5 and 4.25 respectively. Chimaera monstrosa pancreatic chitinase had a very strong optimum around pH 8 to 10, and one less strong at pH 3. These enzyme activities could not be separated by gel filtration or isoelectric focusing. The pI (isoelectric point) was approximately 4.9 for both enzymes. The molecular weight of the C. monstrosa pancreatic chitinase was estimated to be approximately 43 000. Lysozyme activity was absent or extremely weak in the material studied.

Bovine serum chitinase.

Abstract: 1 A glycol-chitin-splitting enzyme without lysozyme (muramidase) activity has been found in calf serum. The enzyme also degrades colloidal chitin and is thus a true chitinase, 1,4-β-poly-N- acetylglucosaminidase, without exo-β-N-acetylglucosaminidase effect. 2 The enzyme is purified 1000-fold by ion-exchange chromatography and gel filtration. Its optimal activity is between pH 1.5 – 2.0 with glycol chitin and between pH 3 – 6 in a rather broad optimum with colloidal chitin as substrate. The optimal stability of the enzyme is in the pH interval 3.0–6.5 when tested by incubation with glycol chitin at 50 °C for 60 min. The optimal temperature for the degradation of glycol chitin is 40°C when assayed at pH 1.5 and 51°C when assayed at pH 3.5. 3 The enzyme is activated by moderate heating at pH < 6.5. The highest relative activity, 135%, is reached after 45 rnin incubation at 30°C, pH 5 or after 30 rnin at 40°C, pH 2.4. By incubation with small amounts of trypsin at pH 6.5 at 37°C the enzyme was temporarily activated. 4 The isoelectric point, PI 5.3, and the molecular weight, 47000 ± 3000 were determined by respectively isoelectric focusing and gel filtration. 5 The Michaelis-Menten constant, Km= 0.76 ± 0.05 (S.E.) mg/ml, was measured with glycol chitin as substrate.

Chitin-binding hemagglutinin produced by Conidiobolus strains.

Abstract: A hemagglutinin was produced by strains of Conidiobolus which also produce beta-N-acetylglucosaminidase. Activity of the hemagglutinin was inhibited by D-glucosamine, N-acetyl-D-glucosamine, D-mannosamine, and beta-N-acetyl-D-glucosaminides but not by D-glucose, D-mannose, and alpha-N-acetyl-D-glucosaminides.

β-1,3-Glucanase and dimorphism in Paracoccidioides brasiliensis

Abstract: Mycelial and yeast forms of P. brasiliensis were tested for several glucohydrolases. In addition to high levels of β-blucanases, low amounts of α-glucanase, chitinase and maltase were found. Tests for invertase, amylase and lactase were negative. The levels of β-1,3-glucanase were higher in the mycelial form. The shift to the mycelial phase correlated with an increase in the levels of β-1,3-glucanase. The enzyme was present in the cytoplasm, cell wall and culture medium. The extracellular enzyme was purified 42 fold by ammonium sulphate precipitation and gel filtration. Maximal activity was obtained at 60°C and pH of 5.0 acetate buffer or pH 6.0 (phosphate buffer). Its Km was 0.205 mg/ml. The cell wall-bound enzyme showed a higher temperature optimum. Optimum pH and Km were also slightly different. Following treatment of the cell walls with chitinase, β-1,3-glucanase was released into the medium.

The effect of beta-glucuronidase and chitinase on the cell wall of Aspergillus niger and Aspergillus fumigatus.

Abstract: The effects of beta-glucuronidase and chitinase have been tested on the hydrolysis of the cell walls of the economically important fungi, Aspergillus niger and Aspergillus fumigatus. The extent of wall hydrolysis was measured by assaying for total reducing sugars, N-acetyl sugars and protoplast production. Maximum reducing sugar release was attained after 40 min incubation, both with beta-glucuronidase supplemented with chitinase and beta-glucuronidase alone, whereas N-acetyl sugar release reached a maximum at 80 min incubation. beta-Glucuronidase was effective in releasing protoplasts from both species of Aspergillus. This release was enhanced by adding chitinase to the incubation medium at 0 and 20 min, but with addition at 60, 80 and 100 min increase in protoplast yield was much reduced. The results of re-incubation experiments with chitinase suggest that this enzyme may in some way be inhibited during the later stages of incubation. Pronase used in combination with beta-glucuronidase slightly enhanced protoplast release.

Microflora in the alimentary tract of gray mullet. V. Studies on the chitinolytic enzymes of Enterobacter and Vibrio.

Abstract: Crude chitinase preparations were obtained from cultural filtrates of Enterobacter and Vibrio which were isolated from the intestinal tract of gray mullet (Mugil cephalus). The Enterobacter preparations after overnight dialysis lost virtually all chitinase activity whereas the enzymic activity of Vibrio preparations did not decrease during similar dialysis. The addition of calcium ions prevented the loss of chitinase activity during dialysis in Enterobacter preparations. Calcium chloride was the best co-factor, among all the chemicals tested. Using calcium chloride it was possible to isolate two different chitinases from Enterobacter by polyacrylamide gel electrophoresis. The Vibrio preparations showed only one band in the absence of calcium chloride. The enzyme preparations from Enterobacter lost its activity at 50°C and the Vibrio preparations did not lose its activity at similar temperature.