Concentration of pyruvic decarboxylase preparation from bakers' yeast unusually affected the enzymic activity. Therefore, theoretical analysis was attempted on the interrelation between the concentration of the enzyme preparation and enzymic activity. Following four situations of the reactions were postulated for the analysis : (1) The enzyme preparation contains inhibitor which reversibly combines with active enzyme. (2) The preparation contains activator which reversibly combines with enzyme. (3) The preparation is consisted of two enzymes which catalyze serial two reactions. (4) The preparation is consisted of two enzymes, and the substrote-enzyme complex serves the second enzymic reaction as a substrate. The interrelations are expressed by quadratic equations. The situations of (1), (2) and (4) are represented by hyperbolas or by parabolas, and that of (3) by two straight lines. The interrelations appeared in pyruvic decarboxylase preparations were explained by combination of the situations (1) and (3), indicating plural components, dissociable inhibitor and independent two enzymes. The possibility of the plural components in pyruvic decarboxylase preparation from bakers' yeast was also indicated by DEAE-cellulose column chromatography and by gel filtration with Sephadex G-100.
