ABSTRACT
Cathepsin B from Helicoverpa armigera (HCB) belongs to the group of cysteine proteinases. HCB is proved being involved in the degradation of yolk proteins during embryonic development,which is an acidic preferring enzyme and is resistant to SDS. The expression of the proenzyme may offer a model for investigating the activation of the enzyme. The HCB gene was constructed into pPIC9K and expressed in Pichia pastoris KM71 strain . After induction by methanol, HCB was expressed and secreted into the medium. The molecular weight of the recombinant procathepsin B was determined as about 38 kDa. The expressed product was confirmed to be HCB by immunoblotting assay using specific rabbit anti-HCB polyclonal antibody. The activity of the product was assayed by in situ hydrolysis (gelatin-SDS-PAGE). These results showed that HCB with proteolytic activity was expressed in P. pastoris KM71. This proenzyme can be used for further research on the activation of the proenzyme or industrial production.