The Proteolytic Enzymes of the K-1 Strain of Streptomyces griseus Obtained from a Commercial Preparation (Pronase)

Abstract

Abstract A homogeneous serine protease, homologous with bovine chymotrypsin, purified from a commercial preparation (Pronase) of the K-1 strain of Streptomyces griseus demonstrated marked stability in the presence of 6 m guanidinium chloride. In this solvent the enzyme was active against N-α-acetyl-l-tyrosine ethyl ester showing a slight increase in Km but a significant decrease in Vmax as compared to results of studies in the absence of denaturant. The rate of hydrolysis of casein was enhanced in the presence of 6 m guanidinium chloride. Ovalbumin, which was minimally hydrolyzed in the absence of denaturant was extensively hydrolyzed by the enzyme in the presence of denaturant. These results probably reflect the selective unfolding of the substrate proteins by denaturant. The enzyme revealed no difference in circular dichroism spectra in the presence or absence of 6 m guanidinium chloride. Sodium ethylenediaminetetraacetate in the presence of denaturant caused a sustained irreversible loss of activity associated with a change in the circular dichroism spectrum. In the absence of guanidine, minimal effects of the chelating agent were seen. These results suggest the probable stabilizing effect of a cation. We believe this is the first demonstration of conservation of enzymatic activity in the presence of 6 m guanidinium chloride. This protease may be useful for structural studies of polypeptides which are, in the native state, resistant to proteolysis.