Chitinase from the extract of pupae of Pieris rapae crucivora Boisduval was purified through the successive steps of CM-Sephadex C-50 ion exchange chromatography and gel filtration chromatography with Sephadex G-150 from crude enzyme extract. Then the active fractions named Chi-A and Chi-B were obtained. The purity of the enzyme increased up to 12.4- and 2.17-fold and the recovery of the enzyme activity were 42.4 and 4.58%, for the fraction Chi-A and Chi-B, respectively. The homogeneity and molecular weight of isolated Chi-A were evaluated by SDS-PAGE. The homogeneity of Chi-A was confirmed as a single band on SDS-PAGE and the molecular weight was estimated to be 48,000. The purified Chi-A had an optimal pH of 5.0 for the hydrolysis reaction when glycol chitin was used as a substrate. Chi-A was stable in the pH range of 4.0-8.0 and retained its 70% activity at 310 K. The chitinase from pupae of Pieris rapae crucivora Boisduval exhibited typical Michaelis-Menten type kinetics. The kinetic parameters for the hydrolysis reaction with glycol chitin by Chi-A were determined to be 1.43 x 10(-2) kg/(m(3).h) as V-max and 23.9 kg/m(3) as K-m at 310 K. We also found that Chi-A revealed a chitin synthase activity. A large amount of N-acetylchitopentaose was efficiently formed by the transglycosylation from N-acetylglucosamine with Chi-A.