ornithine catabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the breakdown of ornithine, an amino acid only rarely found in proteins, but which is important in living organisms as an intermediate in the reactions of the urea cycle and in arginine biosynthesis. [GOC:jl, ISBN:0192801023]

Ornithine catabolism is a crucial metabolic pathway that involves the breakdown of ornithine, a non-protein amino acid, into urea and glutamate. This process primarily takes place in the liver and plays a vital role in nitrogen excretion, detoxification, and amino acid metabolism.

The ornithine catabolic process is initiated by the enzyme ornithine aminotransferase, which converts ornithine into glutamate-γ-semialdehyde. This intermediate is then oxidized by glutamate-γ-semialdehyde dehydrogenase to form glutamate. The glutamate can then be used for various metabolic purposes, such as protein synthesis or energy production.

However, the primary fate of glutamate in the ornithine catabolic pathway is its conversion into α-ketoglutarate, an important intermediate in the citric acid cycle. This conversion is catalyzed by glutamate dehydrogenase.

The remaining nitrogen from ornithine is excreted as urea. Urea is synthesized in the urea cycle, a series of reactions that occur mainly in the liver. The urea cycle incorporates ammonia, which is produced during amino acid catabolism, into urea for excretion.

The ornithine catabolic process is tightly regulated to maintain nitrogen balance and prevent the accumulation of toxic ammonia. Several factors can influence the activity of the enzymes involved, including substrate availability, hormonal signals, and dietary intake.

In summary, ornithine catabolism is a complex metabolic pathway that involves the breakdown of ornithine, the production of glutamate, the excretion of urea, and the regulation of nitrogen balance. It is an essential process for maintaining cellular homeostasis and overall health.'
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Proteins (1)

Compounds (4)