PMID: 1396Jan 25, 1976

Purine nucleotide cycle. Evidence for the occurrence of the cycle in brain.

The Journal of Biological Chemistry
V Schultz, J M Lowenstein


Cell-free extracts of rat brain catalyze the reactions of the purine nucleotide cycle. Ammonia is formed during the deamination but not the amination phase of the cycle. The activity of adenylate deaminase in brain is sufficient to account for the maximum rates of ammonia production that have been reported. The activity of glutamate dehydrogenase is not sufficient to account for these rates of ammonia production. The activities of adenylosuccinate synthetase and adenylosuccinase are nearly sufficient to account for the steady state rates of ammonia production observed in brain. Demonstration of the cycle in extracts of brain is complicated by the occurrence of side reactions, in particular those catalyzed by phosphomonoesterase, nucleoside phosphorylase, and guanase.

Related Concepts

Adenine Nucleotides
Adenosine Deaminase
Adenylate KINASE
AMP Deaminase
Guanine Deaminase
Guanine Nucleotides
Hydrogen-Ion Concentration
Inosine Nucleotides

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