A preliminary characterization of alkaline digestive proteases in the posterior midgut of the face fly, Musca autumnalis De Geer

Alkaline proteases in the posterior midgut of the face fly, Musca autumnalis De Geer, were identified using specific synthetic substrates and nonspecific substrate azocasein. Identification was confirmed with potential protease activators and inhibitors. Optimal azocasein hydrolysis occurred at pH 8.0 and substrate hydrolysis was inhibited by EGTA (ethyleneglycol-bis-(2-aminoethyl ether)-N,N-tetraacetic acid), tosyl-L-lysine chloromethyl ketone (TLCK), and soybean trypsin inhibitor (STI). Tryptic proteolysis was identified by maximal hydrolysis, at pH 8.0, of trypsin specific substrates BAPNA (benzoyl-DL-arginine-p-nitroanilide) and TAME (tosyl-L-arginine methyl ester). TAME hydrolysis was inhibited by PMSF (phenylmethylsulfonyl fluoride), STI, pepstatin A, and dithiothreitol (DTT), but BAPNA hydrolysis was inhibited only by STI and DTT. Chymotrypsin was demonstrated by maximal hydrolysis of BTEE (benzoyl-L-tyrosine ethyl ester) at pH 8.0 and DTT, PMSF, and STI inhibited hydrolysis of this substrate. Amin...