An Inactive Precursor of Streptococcal Proteinase* by Stuart

In a previous report (1) it was shown that, under suitable conditions, some strains of group A streptococci produce in broth cultures an extracellular proteolytic enzyme. In certain respects the enzyme resembles papain and the cathepsins in that it achieves maximal activity under reducing conditions and is inactivated by iodoacetic acid. In broth cultures the reducing conditions necessary for the enzymatic activity are brought about by the presence of living microorganisms and under such conditions the proteinase attacks some of the products of bacterial metabolism, notably the type-specific streptococcal M antigen. Production of the proteinase by streptococci depends to some extent upon the conditions under which they are cultivated. The type of peptone incorporated in the medium has a marked effect in this regard: Thus, while Pfanstiehl and proteose peptone favor production of the enzyme, in neopeptone broth most strains produce only minimal concentrations of the proteinase. More recent experience with the peptone dialysat~ broth described by Dole (2) has shown that, unlike the undialyzed peptone, dialysate of Pfansfiehl peptone does not favor production of the enzyme. In examining these facts in further detail, it was found that the addition of an experimental commercially produced prorein hydrolysate 1 to the neopeptone or to the peptone dialysate broths resulted in increased production of proteinase by the streptococci. Furthermore, addition of the protein hydro]ysate to inactive filtrates prepared from cultures grown in either neopeptone broth or peptone dialysate broth resulted in the appearance of the streptococcal proteinase which, presumably, had previously been present in an inactive form. When the protein hydrolysate was found to contain a small amount of trypsin, these findings immediately suggested an analogy with the activation of trypsinogen and chymotrypsinogen by trypsin. Further experiments were therefore carried out to determine whether streptococcal proteinase is first formed in cultures as an inactive precursor and to study the behavior and mode of activation of this form of the enzyme.