In 1983, during research on soy sauce, YAMASA CORPORATION discovered that some Streptomyces species produce glutamate oxidase, which specifically acts on L-glutamate.
L-glutamate oxidase (EC 1.4.3.11) is an enzyme that catalyzes oxidative deamination of the α-amino group of L-glutamate to 2-ketoglutarate, with concomitant reduction of molecular oxygen and water to ammonia and hydrogen peroxide. L-glutamate oxidase is a member of the general oxidoreductase family, which catalyzes the CH-OH group of the substrate and uses NAD+ or NADP+ as the cofactor. The systematic name of this enzyme class is L-glutamate:oxygen oxidoreductase (deaminating), which is also called glutamate (acceptor) dehydrogenase, glutamate oxidase, glutamic acid oxidase, glutamic dehydrogenase (acceptor) or L-glutamic acid oxidase.
L-glutamate, the substrate of the reaction catalyzed by L-glutamate oxidase, has a flavor-enhancing property that creates the sensation of “umami”, and the monosodium salt of L-glutamate is widely used as a seasoning for cooking and as a food additive. Since the L-glutamic acid content of foods can be readily determined by means of a kit or a sensor employing L-glutamate oxidase, this enzyme is now indispensable in the field of compositional analysis of foods.
Moreover, L-glutamate is also the principal excitatory neurotransmitter in the brain. Furthermore, the excessive release of this amino acid may play a pivotal role in the neuronal death associated with different neurological disorders. Therefore, L-glutamate and L-glutamate oxidase play important roles in clinical biochemistry. In the field of cerebral nerve science, attempts to analyze L-glutamic acid have been energetically pursued by use of a microdialysis and a microsensor in combination. Most enzymes employed in the sensor are L-glutamate oxidases.