Abstract
The proteolytic enzyme from midgut epithelia of the silkworm, Bombyx mori was solubilized with Lubrol WX, partially purified and characterized. The solubilized protease coincided with digestive fluid protease-6B2 in its elution position on a Sepharose 6B column, which suggests the conversion of the former into the latter in vivo. The purified protease rapidly hydrolyzed Hammarsten casein but hydrolyzed serum albumin very slowly. The optimum pH of this enzyme was 11.3, and Km value was estimated as 0.83 mg/ml. The protease activity was strongly inhibited by DFP, PMSF [phenylmethyl sulfonyl fluoride] and TLCK [1-chloro-3-tosylamido-7-amino heptanone] but was not sensitive to EDTA or IAA. It appears to be a serine-type protease having a histidine at the active site of trypsin. The tissue protease was similar to the digestive fluid protease-6B2 in the MW, substrate specificity and effect of inhibitors. The relationship between proteases from the midgut lumen and epithelia is discussed.