The asymmetric distribution of enzymic activity between the six subunits of bovine liver glutamate dehydrogenase. Use of d- and l-glutamyl α-chloromethyl ketones (4-amino-6-chloro-5-oxohexanoic acid)

Abstract

A method for the preparation of D- and L-glutamyl .alpha.-chloromethyl ketones is described. These chloromethyl ketones irreversibly inactivated bovine glutamate dehydrogenase, whereas several other related compounds had no adverse effect on the activity of the enzyme. The inactivation process was due to the modification of lysine-126. The time-courses for the inactivation and the incorporation of radioactivity from tritiated L-glutamyl .alpha.-chloromethyl ketone into the glutamate dehydrogenase were biphasic. The results suggest the involvement of ''negative co-operative'' interactions in the reactivity of lysine-126. The cumulative evidence suggests that the 1st subunit of the enzyme, which takes part in catalysis, makes the largest, and the last the smallest, contribution to the overall catalysis. Three of the 6 subunits of the enzyme may possess as much as 80% of the total activity of bovine glutamate dehydrogenase.