Abstract
The existence of the inactive precursors of yeast proteinases B and C was confirmed in the autolysate of baker's yeast and they were named as pro-proteinases B and C, re-spectively. The active and inactive forms of proteinase C were two distinct proteins, separable by chromatographical procedures. The two precursors were markedly activated by incubation at pH 5 or by treatment with denaturing agents, e. g. urea, dioxane, acetone and certain alcohols.
These activations were also observed with extracts from acetone-dried cells and from mechanically destructed cells, but the activation of proteinase A was not demonstrated under any conditions tested. Therefore, it was assumed that most of proteinases B and C exist in vivo as inactive precursors, whereas proteinase A originally exists in an active form.
