抄録
An endopeptidase which hydrolyzed myofibril strongly from the pyloric caeca of Pacific mackerel Scomber japonicus was purified to homogeneity electrophoretically. The molecular weight and the optimum pH of the endopeptidase was about 30k and around 9.5, respectively. Since the endopeptidase was not inhibited by serine protease inhibitors, e. g. PMSF and soybean trypsin inhibitor, but completely inhibited by E-64, a high specific cysteine protease inhibitor, it was considered to be a cysteine endopeptidase. This is the first report on the existence of the cysteine endopeptidase in the pyloric caeca. The endopeptidase showed a hydrolytic specificity for MCA-synthetic peptide substrates which had a basic amino acid at P1 position and a hydrophobic amino acid at P2 or P3 position. It hydrolyzed various proteins examined except for collagen.
