A prolyl endopeptidase of Sarcophaga peregrina (flesh fly): Its purification and suggestion for its participation in the differentiation of the imaginal discs

A prolyl endopeptidase that hydrolyses Suc-Gly-Pro-MCA (Sue, succinyl; MCA, methyl-coumaryl-7-amide) was purified to near homogeneity from NIH-Sape-4 cells derived from the flesh fly (Sarcophaga peregrina). The molecular mass of the purified enzyme was 84 kDa, and its activity was inhibited almost completely by 1 mM diisopropyl fluorophos-phate (DFP). Immunoblotting and DFP-labeling experiments revealed that the leg imaginal discs of Sarcophaga contained this enzyme as a major serine proteinase. This prolyl endopeptidase is suggested to be involved in the differentiation of imaginal discs, because 2 mM DFP and 0.1 mM N-benzyloxycarbonyl-thioprolyl-thioprolynal-dimethylacetal (ZTTA), a specific inhibitor for prolyl endopeptidase, inhibited differentiation of the imaginal discs from the eversion to the elongation stage.