PURIFICATION AND PROPERTIES OF THE CHYMOTRYPSIN-LIKE SERINE PROTEINASE OVERPRODUCED BY STREPTOMYCES SP STRAIN C5-A13

The major serine proteinase of Streptomyces sp. strain C5-A13, a proteinase-overproducing mutant strain, was purified to homogeneity. It has a relative molecular mass (M(r)) of 19500 as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Superose-6 gel filtration chromatography, a low isoelectric point, optimal activity at pH 8.5-9.5, and an optimal temperature of approx. 55-degrees-C. This purified enzyme has a high specific activity on azocasein of 11000 units . mg-1 of protein, a K(m) of 2.7 x 10(-5) M and a V(max) of 2.0 mumol . min-1 . mg-1 of protein when succinyl-alanyl-alanyl-prolyl-phenylalanine p-nitroanilide was used as substrate. It was inhibited by the serine proteinase inhibitors diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride but not by ethylenediaminetetraacetate (EDTA) or N-tosyl-L-phenylalanine chloromethyl ketone. Thus, this serine proteinase appears to be a chymotrypsin-like enzyme and represents nearly 90% of the total extracellular azocasein-hydrolyzing activity produced by strain C5-A13. Since CaCO3 did not stimulate activity of the purified enzyme itself, the carbonate effect may be a transcriptional or translational rather than a post-translational one.