The effect of metal ions on the hydrolysis of L-asparagine by L-asparaginase

A variety of main group and transition metal ions have been studied as moderators of the enzymatic hydrolysis of L-asparagine by L-asparaginase. The greater deactivations were produced by mercury(II), copper(II) or tetrachloropalladate(II) ions when each moderator was incubated with the enzyme before the hydrolysis reaction was initiated. Different results were observed for copper(II) and mercury(II) when the moderator was incubated with the substrate before adding the enzyme; in this latter situation the copper(II) ion appears to act as a co-factor for the reaction. It has been shown that in the presence of each of the metal ions chosen the energy of activation of the moderated enzymatic hydrolysis reaction remains unchanged from that of the control reaction.