Purification and characterization of a hemocyte proteinase of Sarcophaga, possibly participating in elimination of foreign substances

We have reported that foreign protein injected into the abdominal cavity of Sarcophaga peregrina (flesh fly) larvae is degraded in the hemolymph by a proteinase secreted by hemocytes [Suzuki, T. and Natori, S. (1985) Comp. Biochem. Physiol. 81A, 191–193]. Here we report the purification and characterization of a proteinase from larval hemocytes. This enzyme is a cysteine proteinase consisting of 26‐kDa and 29‐kDa subunits with similar substrate specificity to mammalian cathepsin B. This enzyme was shown to be released from hemocytes into the hemolymph of larvae following injection of sheep red blood cells into the larvae, suggesting that it participates, at least in part, in elimination of foreign substances introduced into the body cavity.