A novel chitinase isolated from Vicia faba and its antifungal activity

A novel chitinase with antifungal activity was isolated from fava bean (Vicia faba) seeds. The protein exhibited a molecular mass of 21.5 kDa in reduced condition while 25.5 kDa in oxidized condition on SDS-PAGE, indicating that there are disulfide bonds inside the molecule. Its N-terminal amino acid sequence was determined to be D-D-V-G-S-V-I-S-A-S-L-F-E-Q-L-L-K-H, showing homologous to those of chitinase and chitinase precursors from leguminous plants. The optimum pH and the optimum temperature for activity toward N-acetyl-d-glucosamine were 5.4 and 50 °C, respectively. The pI was determined to be 8.7 by isoelectric focusing electrophoresis. The chitinase was thermostable up to 58 °C in both enzymatic reaction and antifungal activity. It showed chitin-binding activity, suggesting that the catalytic domain is involved in the binding of chitinase to a certain extent. In addition, it exerted potent antifungal action toward a variety of fungal species including Pythium aphanidermatum, Fusarium solani, Physalospora piricola, Alternaria alternate, Botrytis cinerea, and Fusarium oxysporum f. sp. melonis. The present findings demonstrated a novel chitinase with disulfide bonds inside the molecule and show antifungal significance in agriculture.

► The chitinase is a monomeric protein and there are disulfide bonds inside the molecule. ► The chitinase was thermostable up to 58 °C in enzymatic reaction and antifungal activity. ► The activity was severely inhibited by Cu2+, Fe2+, Pb2+ and Hg2+. ► The chitin-binding activity is involved in the catalytic process of chitinase. ► The N-terminal sequence shows resemblance to chitinase precursors from other plants.