Summary
An extracellular protease SN 687, secreted by the soil bacterium isolate WM 122, has
been purified by means of gel filtration, ammonium sulfate precipitation, DEAE-Sephadex
and hydroxylapatite chromatography. Apparent homogeneity was ascertained by Polyacrylamide
gel electrophoresis. The protease was inactivated by ethylenediamine tetracetic acid
(EDTA) but not by diisopropylfluorophosphate (DFP), and it was partially inhibited
by serum inhibitors. SN 687 was shown to be of high specific activity against casein
and fibrin, but it did not hydrolyze L- lysine -methyl ester dihydrochloride (LME),
p-tosyl-L-arginine-methyl ester hydrochloride (TAME) and N-benzoyl-L-tyrosine-ethyl
ester hydrochloride (BTEE) synthetic substrates. The optimum pH for hydrolysis of
casein was 7.5 and the molecular weight, as determined by gel filtration, was 31,000.
