Studies on Proteases in Submaxillary Gland. I. Fractionation and General Characteristics of Rat Submaxillary Proteases.

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Abstract
By chromatography on DEAE-cellulose column, 5 protease fractions were separated from the rat submaxillary gland, and tentatively named rat submaxillary protease A, B, C, D and E. The casein-hydrolyzing activities of the protease A, B, C, D and E were optimal at pH 8.3, 10.2, 9.6, 8.3 and 9.6 respectively. The rat submaxillary proteases were most stable at neutral pH, and were not affected by the addition of EDTA, rat submaxillary dialyzate, monoidoacetate or p-chloromercuribenzoate. All 5 proteases were inactivated by diisopropyl fluorophosphate. The activities of protease A, B and E were not inhibited by soybean-trypsin-inhibitor, whereas chymotrypsin-type inhibitions were observed in the cases of the protease C and D. The protease A had no less milk-clotting activity than that of chymotrypsin, while the protease B expressed about one-tenth activity of that of chymotrypsin, and only neglectable activities were observed in the cases of the protease C, D and E.