A thermostable chitinase with chitin-binding activity from Phaseolus limensis

A 28.6-kDa chitinase with chitin-binding activity was isolated from the large lima bean (Phaseolus limensis) seeds. The procedure entailed extraction, ammonium sulfate precipitation, affinity chromatography on Affi-gel blue gel, and high-performance liquid chromatography (HPLC) on SP-Toyopearl. There was an almost 108-fold increase in specific activity of the purified chitinase compared with that of the crude extract. The enzyme exhibited a pI of 7.8 by isoelectric focusing electrophoresis. The optimum pH and the optimum temperature for activity toward N-acetyld-glucosamine were 5.4 and 40 to 50 degrees C, respectively. The enzyme was stable up to 55 degrees C. It exerted a potent inhibitory action toward fungal species, including Fusarium solani, Pythium aphanidermnatum, and Sclerotium rolfsii.