[Influence of glutathione on the catalytic properties of leucine aminopeptidase].

1. Leucine aminopeptidase does not catalyze the hydrolysis of glutathione. 2. Glutathione inhibits the hydrolysis of the substrates leucine hydrazide and leucine-p-nitroanilide by leucine aminopeptidase. 3. By means of kinetic experiments the type of the inhibition has been determined as noncompetitive. The inhibition constant Ki for the Mg2+-activated enzyme is five times higher than for the non-activated enzyme. 4. The degree of inhibition caused by glutathione depends on the pH value indicating a competition between glutathione and OH- ions. Mg2+-activated enzyme is invariably inhibited in the investigated pH range of 7.2 to 9.8. 5. A preincubation of the enzyme with glutathione changes the degree of activity enhancement by metal ions.