Abstract:

In order to investigate the essential groups for peroxidase (POD) activity from jackfruit flesh, diacetyl, N-ethyl-
N’-3-dimethylaminopropylcarbodiimide (EDC), N-acetylimidazole (NAI), β-mercaptoethanol(MT), parachloro-mercuribenzoate
(pCMB) and diethyl pyrocarbonate (DEPC) were used to modify the POD enzyme. The results revealed that
diacetyl, EDC and NAI showed no significant impact on POD activity, indicating that Arg, carboxyl and Lys had no
association with the enzyme activity. However, pCMB, DEPC and MT strongly inhibited POD activity, indicating that Cys
and His were the essential groups for its activity, and disulfide bond played a very important role in the enzyme activity.
Enzymatic kinetics and substrate protection indicated that DEPC was a competitive inhibitor for POD, and the His residue
was located at the enzyme active center.

Key words: peroxidase, jackfruit, enzyme activity center, essential group, chemical modification