Abstract
Three chitinases (EC 3.2.1.14) were purified from yam, Dioscorea opposita Thumb, by fractionation with ammonium sulfate, chromatographies on DEAE-Cellulose and DEAESephadex A-50, chromatofocusing and gel filtration on Bio-Gel P-60. The purified enzymes (E-l, E-2 and E-3) showed single bands on sodium dodecylsulfate polyacrylamide gel electrophoresis, and the molecular weights were estimated to be 33, 500. The pis were 4.05 (E-l), 4.0 (E-2) and 3.8 (E-3). All enzymes were glycoproteins and the neutral sugar contents were 3.6% (E-l), 3.6 (E-2) and 0.9% (E-3). The N-terminal amino acids ofE-l and E-3 were the same and determined to be histidine. All enzymes hydrolyzed glycolchitin, but not p-nitrophenyl-2-acetamido-2-deoxy-β-D-glucopyranoside or Micrococcus lysodeikticus cell walls. E-l and E-3 were stable in the pH range of 5-11, and below 60°C. These enzymes showed two optimum pHs around 3.5 and 8.0 or 8.5 with glycolchitin as substrate.
