Glutamate dehydrogenase (NADP+)

Glutamate dehydrogenase (NADP+), often abbreviated as GDH (NADP+), is an enzyme belonging to the oxidoreductase class. Specifically, it catalyzes the reversible oxidative deamination of L-glutamate to α-ketoglutarate using NADP+ as a coenzyme. The reaction also produces ammonia (NH3) and NADPH.

The enzyme’s systematic name is L-glutamate:NADP+ oxidoreductase (deaminating). It is analogous to glutamate dehydrogenase (NAD+), which uses NAD+ as a coenzyme instead of NADP+.

This enzyme plays a significant role in nitrogen metabolism by interconverting glutamate, a central amino acid, and α-ketoglutarate, an intermediate in the citric acid cycle. The generated ammonia can then enter the urea cycle for detoxification. The direction of the reaction, i.e., glutamate synthesis versus glutamate degradation, is primarily dictated by the concentrations of substrates and products.

GDH (NADP+) is found in various organisms, including bacteria, plants, and animals, although its relative abundance and specific roles can vary depending on the organism and tissue. In some organisms, it plays a crucial role in glutamate biosynthesis, particularly under conditions where ammonia assimilation is essential. Conversely, in others, it functions primarily in glutamate degradation.

The enzyme is often regulated by various factors, including cellular energy charge and the availability of substrates. Allosteric effectors, such as ADP and GTP, can modulate its activity. Disruptions in glutamate dehydrogenase activity have been linked to several metabolic disorders and neurological conditions.