Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Profiles of the catabolism of adenine nucleotides in cultured plant cells were investigated. Adenine nucleotides, prelabelled by incubation of suspension-cultured Catharantus roseus cells with [8-14C]adenosine, were catabolized rapidly and most of the radioactivity appeared in 14CO2. Allantoin and allantoic acid, intermediates of the oxidative catabolic pathway of purines, were temporarily labelled. When the cells, prelabelled with [8-14C]adenosine, were incubated with high concentrations of adenosine, the rate of catabolism of adenine nucleotides increased. The results suggest that the relative rate of catabolism of adenine nucleotides is strongly dependent on the concentration of adenine nucleotides in the cells. Studies using allopurinol, coformycin and tiazofurin, inhibitors of enzymes involved in purine metabolism, suggest that participation of AMP deaminase and xanthine oxidoreductase in the catabolism of adenine nucleotides in plant cells. AMP deaminase was found in extracts from C. roseus cells and its activity increased significantly in the presence of ATP. In contrast, no adenosine deaminase or adenine deaminase activity was detected. Qualitative differences in the catabolic activity of AMP were observed between suspension-cultured cells from different species of plants.
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PMID:Catabolism of adenine nucleotides in suspension-cultured plant cells. 201 71

Our earlier work on reperfusion showed that adult rat hearts released almost twice as much purine nucleosides and oxypurines as newborn hearts did [Am J Physiol 254 (1988) H1091]. A change in the ratio anabolism/catabolism of adenosine could be responsible for this effect. We therefore measured the activity of adenosine kinase, adenosine deaminase, nucleoside phosphorylase and xanthine oxidoreductase in homogenates of hearts and myocytes from neonatal and adult rats. In hearts the activity of adenosine deaminase and nucleoside phosphorylase (10-20 U/g protein) changed relatively little. However, adenosine kinase activity decreased from 1.3 to 0.6 U/g (P less than 0.025), and xanthine oxidoreductase activity increased from 0.02 to 0.85 U/g (P less than 0.005). Thus the ratio in activity of these rate-limiting enzymes for anabolism and catabolism dropped from 68 to 0.68 during cardiac development. In contrast, the ratio in myocytes remained unchanged (about 23). The large difference in adenosine anabolism/catabolism ratio, observed in heart homogenates, could explain why ATP breakdown due to hypoxia is lower in neonatal than in adult heart. Because this change is absent in myocytes, we speculate that mainly endothelial activities of adenosine kinase and xanthine oxidoreductase are responsible for this shift in purine metabolism during development.
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PMID:Ischemic nucleotide breakdown increases during cardiac development due to drop in adenosine anabolism/catabolism ratio. 209 32

Pathways producing and converting adenosine have hardly been investigated in human heart, contrasting work in other species. We compared the kinetics of enzymes associated with purine degradation and salvage in human and rat heart cytoplasm assaying for adenosine deaminase, nucleoside phosphorylase, xanthine oxidoreductase, AMP deaminase, AMP- and IMP-specific 5'-nucleotidases, adenosine kinase and hypoxanthine guanine phosphoribosyltransferase (HGPRT). Xanthine oxidoreductase was not detectable in human heart. The Km-values of the AMP-catabolizing enzymes were 2-5 times higher in human heart; the substrate affinity of the other enzymes was in the same order of magnitude in both species. The maximal activity (Vmax) of adenosine kinase was the same in both species, but HGPRT in man was only 12% of that in the rat. For human heart the Vmax-values of adenosine deaminase, nucleoside phosphorylase, AMP- and IMP-specific 5'-nucleotidases, and AMP deaminase were 25-50% of those for rat heart. We conclude that human heart is less geared to purine catabolism than rat heart as is evident from the lower activities of the catabolic enzymes. Maintenance of the nucleotide pool may thus play a more important role in human heart.
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PMID:Kinetics of adenylate metabolism in human and rat myocardium. 759 55

To determine whether interferon-gamma affects rat purine catabolic and salvage enzyme activities, rats were injected with interferon-gamma (600000 U/kg, i.p.) and, similarly to a vehicle-injected control group, killed before or after injection at 6, 12, and 24 h. Organ homogenates were prepared and enzymatic reactions with substrates were carried out, after which the products were measured either chromatographically or spectrophotometrically. Western and Northern blotting also were performed. In contrast to the vehicle-injected rats, interferon-gamma-injected rats showed a significant rise in xanthine oxidoreductase activity in the liver, while enzyme activity was unchanged in the spleen, kidney, and lung. Western analysis of hepatic xanthine oxidoreductase showed an increased concentration of this protein 12 and 24 h after interferon-gamma injection. Northern analysis disclosed an enhanced mRNA expression coding for this enzyme, peaking 12 h after injection. Contrastingly, the activities of adenosine deaminase, purine nucleoside phosphorylase, hypoxanthine guanine phosphoribosyltransferase, and adenine phosphoribosyltransferase were not affected by interferon-gamma in any organ tested. While interferon-gamma causes an increased hepatic biosynthesis of xanthine oxidoreductase, the physiologic role of this enzyme induction remains undetermined.
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PMID:Effect of interferon-gamma on purine catabolic and salvage enzyme activities in rats. 1035 Jun 54