The intracellular distribution, latency and electrophoretic mobility of l-glutamate-oxaloacetate transaminase from rat liver

Abstract

Methods of L-glutamate-oxalo-acetate-transaminase assay (with a -oxoglutarate and L-aspartate as substrates ) have been compared and modified. Maximum activity could be readily achieved only with the assay system of the method of Karmen (1955). L-glutamate-oxaloacetate transaminase has been shown to be present in rat-liver mitochondria in latent form. After activation the activity of transaminase in mitochondria is three to four times that in the supernatant fraction. Activation has been achieved by using hypoosmotic media, incubation at 37[degree], storage at 4[degree], treatment with Triton X-100, mechanical disintegration and ultrasonic disintegration. With ultrasonic and mechanical disintegration, but not with hypo-osmotic treatment, this activation is accompanied by re-lease of the enzyme in soluble form. It has been shown that mitochon-drial transaminase differs from supernatant transaminase in its substrate affinities, pH-dependence and electrophoretic mobility. Two L-glutamate-oxaloacetate transminases separated electro-phoretically from rat-liver extract appear to correspond to the mitochondrial and supernatant enzymes respectively. Transamina-tion from L-aspartate is inhibited by the oxaloacetate produced.