What is the role of glutamate dehydrogenase?
Glutamate dehydrogenase (GDH) catalyzes the reversible inter-conversion of glutamate to α-ketoglutarate and ammonia. High levels of GDH activity is found in mammalian liver, kidney, brain, and pancreas. In the kidney, GDH function produces ammonia from glutamate to control acidosis.
What activates GDH?
GDH is activated when amino acids (protein) are ingested to promote insulin secretion and appropriate anabolic effects on peripheral tissues; in the glucose-fed state, GDH is inhibited in pancreas perhaps to redirect amino acids into glutamine synthesis in order to amplify insulin release.
How is ammonia removed from the brain?
When the liver fails to regulate ammonia concentrations, the brain, devoid of a urea cycle, relies solely on the amidation of glutamate to glutamine through glutamine synthetase, to efficiently clear ammonia.
What is the role of glutamic acid dehydrogenase in amino acid metabolism?
Glutamate dehydrogenase plays a major role in amino acid metabolism. It is a zinc protein; requires NAD1 or NADP1 as a coenzyme; and is present in high concentrations in the mitochondria of liver, heart, muscle, and kidney. It catalyzes the (reversible) oxidative deamination of L-glutamate to α-ketoglutarate and NH3.
What is the first step in the action of glutamate dehydrogenase?
The first step in the mechanism for catalytic activity of GDH is the -deprotonation of the alpha-amino group of glutamate by Asp 165, which acts as a general base. Next, a hydride transfer to NAD+ occurs, which forms a Schiff base intermediate (13).
How is glutamate dehydrogenase regulated mammals?
Only in the animal kingdom is this enzyme heavily allosterically regulated by a wide array of metabolites. The major activators are ADP and leucine, while the most important inhibitors include GTP, palmitoyl CoA, and ATP.
Is GDH a transaminase?
Glutamate dehydrogenase (GDH) and the transaminases namely aspartate aminotransferase (AAT) and alanine aminotransferase (AIAT) were estimated in the muscle, liver, kidney, and brain of control and ammonium acetate administered frogs.
Can you recover from high ammonia levels?
In some cases, an elevated blood ammonia level will resolve on its own without treatment. In addition to an increased level of ammonia in the blood, other symptoms of elevated blood ammonia include muscle weakness, fatigue, or other symptoms of liver and kidney damage and failure.
Is glutamate dehydrogenase allosterically inhibited by ATP?
In terms of in-vivo activity, these two regulators essentially act as energy switches for the enzyme. When the mitochondria are at a high-energy state and rich in triphosphates, GDH is inhibited by GTP and, to a lesser extent, ATP.
What is unique about glutamate dehydrogenase?
GDH is unique because it is able to utilize both NAD+ and NADP+ (15). NAD+ is utilized in the reverse reaction, which involves L-glutamate being converted to alpha ketoglutarate and free ammonia via an oxidative deamination reaction (1).
