Purine nucleotide cycle

Protein metabolic pathway

The Purine Nucleotide Cycle is a metabolic pathway in protein metabolism requiring the amino acids aspartate and glutamate. The cycle is used to regulate the levels of adenine nucleotides, in which ammonia and fumarate are generated. AMP converts into IMP and the byproduct ammonia. IMP converts to S-AMP (adenylosuccinate), which then converts to AMP and the byproduct fumarate. The fumarate goes on to produce ATP (energy) via oxidative phosphorylation as it enters the Krebs cycle and then the electron transport chain. Lowenstein first described this pathway and outlined its importance in processes including amino acid catabolism and regulation of flux through glycolysis and the Krebs cycle.

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