THE OXIDATION OF GLUTAMATE BY RAT-LIVER MITOCHONDRIA

Abstract

In rat-liver mitochondria both the dehydrogenase and transaminase routes participate in glutamate oxidation. The rate of ammonia production by the dehydrogenase pathway progressively decreases with the time of incubation. Glutamate deamination is stimulated by blocking the transaminase pathway with arsenite or malonate. On the other hand, this process is completely suppressed by succinate, malate, pyruvate and oxaloacetate. Suc-cinate and pyruvate inhibit, whereas malate and oxaloacetate stimulate, aspartate formation. Glutamate deamination increases with increasing concentrations of 2,4-dinitrophenol from 0.05 to 0.2 m[image], and then becomes inhibited, together with the rate of oxygen consumption. Aspartate formation is progressively inhibited with increasing 2,4-dinitrophenol concentration from 0.05 to 0.8 m[image] In the presence of 0.20 m[image]-2,4-dinitrophenol the rate of ammonia production is higher than in the presence of phosphate acceptors and decreases much slower and linearly with the time of incubation. The addition of nicotinamide adenine dinucleotide (NAD+) enhances glutamate deamination without affecting oxygen uptake.