Relationship between alkaline proteases from the midgut lumen and epithelia of the silkworm: Partial purification and comparison of properties of both proteases-6B3

Abstract

1. 1. Midgut epithelial protease of the silkworm, Bombyx mori was solubilized, partially purified and compared with the properties of corresponding lumenal protease-6B3. 2. 2. The optimum pH, pI and K m value for BAPNA of the epithelial protease were 11.4, 10.70 and 0.697 mM respectively. 3. 3. Both epithelial and lumenal enzymes were inactivated by PMSF, leupeptin, STI and LTI, indicating that they are serine-type and trypsin-like proteases. 4. 4. Thiol blocking reagents, PCMB, Cu 2+ and IAA inhibited both proteases. 5. 5. These proteases were different in the effect of PCMB, IAA, STI and some ions. 6. 6. The relationship between epithelial and lumenal proteases is discussed.