Abstract
An investigation has been made to determine the effectiveness of univalent cations as cofactors for the inductive synthesis of nitrate reductase. In these experiments K+ functions more effectively as the univalent cation activator than other univalent cations. Substitution of Rb+ for K+ resulted in enzyme formation at a rate of about one-half of that obtained with K+. Sodium, Li+, or NH4+ either failed to stimulate or completely inhibited the inductive formation of the enzyme. When no univalent cations were present in the induction medium, enzyme formation was delayed for an initial 3-hour period in contrast to the normal one-hour delay in enzyme formation where adequate K+ was present in the induction medium.
During the period of inductive formation of nitrate reductase the activity of pyruvic kinase, a constitutive enzyme, was assayed under conditions where adequate K+ was present. Results indicate that the presence of the different univalent cations in the induction medium had no striking effect on the activity of this enzyme during the induction period.
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