β-Hexosaminidase, an enzyme from ripening bell capsicum (Capsicum annuum var. variata)

beta-Hexosaminidase activity increased significantly during fruit development and ripening of bell capsicum (Capsicuum annuum var. variata). Three isoforms of beta-hexosaminidase from bell capsicum could be resolved upon ion exchange chromatography with step wise gradient (0.10, 0.15 and 0.20 M NaCl) having an abundance of 38, 47 and 15% for isoforms 1, 11 and III respectively. Isoforms I and 11 were further purified on gel permeation chromatography. The pH optimum for these two isoforms was around 5. Isoform 11 exhibited higher thermal stability. Hg2+ and Zn2+ inhibited both, but isoform I showed a much higher inhibition by Cu2+ also. The K-m for isoforms I and 11 with pnp-beta-D-N-acetyl glucosamine pyranoside was 3.00 and 1.75 mM, respectively. Isoform 11 on SDS-PAGE was found to be a monomer with a relative molecular mass of 85 kD. This isoform (the most major) appeared to be electrophoretically homogeneous. beta-Hexosaminidase is novel in the context of fruit ripening. This enzyme has not been reported from fruits and studied hitherto. (C) 2002 Elsevier Science Ltd. All rights reserved.