Effect of inorganic anions on the inhibition of trehalase activity by mercuric chloride

Abstract

Monovalent inorganic anions showed an unexpected effect on the inhibition of trehalase (α,α-trehalose glucohydrolase, EC 3.2.1.28) by SH inhibitors. This phenomeon (deinhibition) was caused by monovalent anions, Cl −, Br −, I − and SCN −. F − and CIO 4 − showed partial deinhibition. Deinhibition was not caused by NO 2 − and SO 4 −. The effectiveness of the ‘active anions’ in causing deinhibition was highly dependent on the anion size. Trehalase in the presence of mercuric chloride was ‘activated’ by Cl −, and the activation was saturable. From the results of Dixon plots for trehalase at different concentrations of the ‘activator’ (deinhibitor) and a constant concentration of the substrate, it can be seen that the activator and the inhibitor competed with each other. Thus, it is suggested that the activator and the inhibitor share a common binding site or bind very near each other. The K i value for mercuric chloride was increased with increasing concentration of NaCl. Therefore, it might be essential to remove the ‘active anions’ in order to determine the inhibitory effect and the K i value of trehalase for SH inhibitors.