Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.17 (adenosine deaminase)
 5,206 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Purine nucleotide cycle. Evidence for the occurrence of the cycle in brain. 0 96

Previous results demonstrated that the adenosine that accumulates in human fat cell suspensions is derived from extracellular sources (Kather, H. (1988) J. Biol. Chem. 263, 8803-8809). To get insight into the mechanisms responsible for the lack of adenosine release, extracellular adenine nucleotide catabolism was minimized by 10 mmol/liter beta-glycerophosphate and 10 mumol/liter alpha,beta-methyleneadenosine 5'-diphosphate. Intracellular adenine nucleotide catabolism resulted in a release of inosine and hypoxanthine under these conditions that was increased markedly by isoproterenol. Experiments with inhibitors of adenosine deaminase and adenosine kinase indicated that the production of inosine and hypoxanthine proceeded via AMP deamination. Consistently, IMP levels were increased transiently in the presence of isoproterenol. In addition, the cells possessed a nucleotide phosphomonoesterase that was resistant to the inhibitory actions of ATP and alpha,beta-methyleneadenosine 5'-diphosphate and showed preference for IMP over AMP. Adenosine (approximately 1 nmol/10(6) cells/h) was also produced inside the cells. However, adenosine production was unrelated to ATP turnover via adenylate cyclase, and any adenosine formed was immediately reconverted to adenine nucleotides in the absence and presence of isoproterenol. It was concluded that adenosine is not released by intact human adipocytes, because the alternative routes of intracellular AMP catabolism are compartmentalized (at least in functional terms), and adenosine kinase is not saturated with substrate in the absence and presence of isoproterenol.
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PMID:Pathways of purine metabolism in human adipocytes. Further evidence against a role of adenosine as an endogenous regulator of human fat cell function. 229 25