Purification and characterization of a chitinase from peanut (Arachis hypogaea L.)

A chitinase was isolated from peanut (Arachis hypogaea L.) seeds. The procedure entailed extraction, ammonium sulfate precipitation, affinity chromatography on Affi-gel blue gel, and high-performance liquid chromatography on POROS 20 HQ. There was a 133-fold increase in specific activity of purified chitinase compared with that of the crude extract. The protein exhibited a molecular mass of 34.4 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis both under reducing and nonreducing conditions, indicating that it is a monomeric protein. The isoelectric point was 5.1 by isoelectric focusing electrophoresis. Optimal pH activity was 5.4 and optimal temperature was 40-50C. The enzyme was stable below 55C, but was rapidly inactivated when incubated at temperatures above 60C. These results demonstrated that the purified protein was a kind of relatively thermostable chitinase from the peanut seeds.