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Abstract

Silkworm moth (bombyx) egg cysteine proteinase with maximal activity at pH 3.0 was purified by chromatography and isoelectrofocusing. On SDS-electrophoresis in polyacrylamide gel the purified enzyme showed a single band of molecular mass 50 kD. Isoelectrofocusing revealed that the bombyx egg cysteine proteinase exists in two forms with pI values of 5.95 and 6.43, respectively. The enzyme activity was sensitive to inhibition by iodoacetamide and p-chloromercuribenzoate but resistant to EDTA, pepstatin, and phenylmethylsulfonyl fluoride. The cysteine proteinase hydrolyzes storage proteins of bombyx eggs but it was inactive with respect to N-benzoyl-D,L-arginine-p-nitroanilide (BAPNA). It is a cathepsin L-like enzyme.

Proteolytic enzymes as markers of productivity and heterosis of silkworm

“…Characteristic of acid cysteine proteinases at the initial stages of postdiapause egg development are high activity levels compared with other proteolytic enzymes [5]. It is the acid cysteine proteinases that play a key role in the metabolism of storage proteins during insect embryogenesis [5,[7][8][9][10]. By the end of spring egg development, the activity of acid cysteine proteinases decreases considerably, which correlates with depletion of the substrate-yolk storage proteins [11].…”