Digestive processes of haematophagous insects. XI. Partial purification and some properties of six proteolytic enzymes from the tsetse fly Glossina morsitans morsitans Westwood (Diptera: Glossinidae)
DEAE-cellulose chromatography, affinity chromatography and Sephadex gel filtration revealed 6 proteolytic enzymes active in alkaline medium in the digestive portion of the midgut (tissue and lumen contents) of adult G. morsitans morsitans. By use of synthetic substrates the enzymes were characterized as aminopeptidase (AP; EC 3.4.11.1), carboxypeptidase A (CPA; EC 3.4.12.2), carboxypeptidase B (CPB; EC 3.4.12.3), trypsin (EC 3.4.21.4), a trypsinlike enzyme designated proteinase VI, and a chymotrypsinlike enzyme designated proteinase VII. By Sephadex G-100 gel filtration the MW were estimated to be 20,000 for trypsin, 19,000 for proteinase VI, 35,500 for proteinase VII, 30,000 for CPA, 22,000 for CPB, and .gtoreq. 100,000 for AP. The Km values (mg/ml) for Hb were 3.43 for trypsin, 2.45 for proteinase VI, 3.68 for proteinase VII, and 2.42 for CPA. The Km values for casein were 1.22 for trypsin and 1.38 for proteinase VII. Casein showed substrate inhibition when hydrolyzed by proteinase VI and VII. Neither Hb nor casein was hydrolyzed by AP and CPB. The pH optima were determined for hydrolysis of casein and the synthetic substrates.