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)

Adenosine kinase (EN 2.7.1.20) from rat and dog heart was purified until it was devoid of adenosine deaminase activity. A stimulation of adenosine kinase activity by dipyridamole was observed when the enzyme was assayed under optimal conditions. At low substrate concentrations adenosine kinase was inhibited by the drug. It increased the Km for adenosine sevenfold. The effects of dipyridamole were Mg2+-dependent. The adenosine-sparing action of dipyridamole at low substrate concentrations is in keeping with the vasodilatory action of the drug.
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PMID:Dipyridamole affects myocardial adenosine kinase activity. 9 42

Purine nucleoside phosphorylase (PNP) deficiency is associated with a severe defect in thymus-derived (T)-lymphocyte function combined with normal bone marrow-derived (B)-lymphocyte function. To investigate the role of this enzyme deficiency in the resulting immune dysfunction, we measured the levels of ribonucleoside and deoxyribonucleoside triphosphates in erythrocytes from two unrelated PNP-deficient, T-lymphocyte-deficient patients. Both PNP-deficient patients have abnormally high levels of deoxyguanosine triphosphate (deoxy-GTP) in their erythrocytes (5 and 8 nmol/ml packed erythrocytes). In contrast, normal controls and adenosine deaminase-deficient, immunodeficient patients do not have detectable amounts of deoxyGTP (<0.5 nmol/ml packed erythrocytes). We propose that deoxyguanosine, a substrate of PNP, is the potentially lymphotoxic metabolite in PNP deficiency. The mechanism of toxicity involves phosphorylation of deoxyguanosine to deoxyGTP, which acts as a potent inhibitor of mammalian ribonucleotide reductase.
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PMID:Deoxyguanosine triphosphate as a possible toxic metabolite in the immunodeficiency associated with purine nucleoside phosphorylase deficiency. 9 38

Rates of purine synthesis de novo, as measured by the incorporation of [14C]formate into newly synthesized purines, have been determined in cultured human fibroblasts derived from normal individuals and from patients deficient in adenosine deaminase, purine nucleoside phosphorylase, or hypoxanthine phosphoribosyltransferase, three consecutive enzymes of the purine salvage pathway. All four types of cell lines are capable of incorporating [14C]formate into purines at approximately the same rate when the assays are conducted in purine-free medium. The purine overproduction that is characteristic of a deficiency in either the transferase or the phosphorylase and that results from a block in purine reutilization can be demonstrated by the resistance of [14C]formate incorporation into purines to inhibition by hypoxanthine in the case of hypoxanthine phosphoribosyltransferase-deficient fibroblasts and by resistance to inhibition by inosine in the case of purine nucleoside phosphorylase-deficient fibroblasts.
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PMID:Purine metabolism in cultured human fibroblasts derived from patients deficient in hypoxanthine phosphoribosyltransferase, purine nucleoside phosphorylase, or adenosine deaminase. 9 41

Purine nucleoside phosphorylase (PNP), the enzyme schematically next to adenosine deaminase in the purine salvage pathway, has been demonstrated cytochemically in peripheral blood lymphocytes of healthy subjects and chronic lymphocytic leukemia (CLL) patients. The enzyme activity is confined to the cytosol. In healthy subjects the majority of lymphocytes are strongly reactive for PNP, whereas the rest are devoid of cytochemically demonstrable activity. The percentage of PNP-positive cells largely corresponds to the number of E rosette-forming cells and is inversely proportional to the number of Ig-bearing cells. In six of seven CLL patients studied only a minor percentage of the lymphocytes showed strong PNP activity, whereas the large majority (88%--98%) possessed trace activity. Such patients have a high number of Ig-bearing cells and a low number of E rosette-forming cells. A different pattern of markers was found in the lymphocytes of the seventh CLL patient: 66% were strongly reactive for PNP, an important number formed E rosettes, and a minor percentage were Ig bearing. These data indicate that PNP can be useful as a "nonmembrane" marker in the differentiation of the B and T cell origin in CLL and deserves to be studied in other lymphoproliferative disorders.
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PMID:Purine nucleoside phosphorylase in chronic lymphocytic leukemia (CLL). 10 Jan 52

Intact cells of Bacillus cereus catalyze the breakdown of exogenous AMP to hypoxanthine and ribose 1-phosphate through the successive action of 5'-nucleotidase, adenosine deaminase, and inosine phosphorylase. Inosine hydrolase was not detectable, even in crude extracts. Inosine phosphorylase causes a "translocation" of the ribose moiety (as ribose 1-phosphate) inside the cell, while hypoxanthine remains external. Even though the equilibrium of the phosphorolytic reaction favors nucleoside synthesis, exogenous inosine (as well as adenosine and AMP) is almost quantitatively transformed into external hypoxanthine, since ribose 1-phosphate is readily metabolized inside the cell. Most likely, the translocated ribose 1-phosphate enters the sugar phosphate shunt, via its prior conversion into ribose 5-phosphate, thus supplying the energy required for the subsequent uptake of hypoxanthine in B. cereus.
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PMID:Utilization of exogenous purine compounds in Bacillus cereus. Translocation of the ribose moiety of inosine. 10 Apr 97

The activity of adenosine deaminase (EC 3.5.4.4.) was significantly lower in lymphocytes from patients with lung cancer than in those from healthy subjects, whereas the activity of purine nucleoside phosphorylase (EC 2.4.2.1.) was significantly higher in lymphocytes from the patients than in those from normal controls. When the one activity was plotted against the other, the plots for patients with lung cancer were all outside the frame formed by the lower and higher limits of the standard deviation of the mean of normal activities of the two enzymes. The ratio of adenosine deaminase activity to purine nucleoside phosphorylase activity was lower in patients with lung cancer than in controls. The possible effect of this ratio on the function of lymphocytes was briefly discussed. These enzyme activities were suggested to be useful measures of the immune responsiveness of patients with lung cancer.
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PMID:Adenosine deaminase and purine nucleoside phosphorylase activities in lymphocytes from patients with lung cancer. 10 12

Activities of adenosine deaminase, adenosine kinase and purine nucleoside phosphorylase were determined in extracts prepared from human skin fibroblast strains derived from 7 normal newborn males and 4 normal adult males. All strains were harvested between passages 9 and 12. Adenosine deaminase activity in adult strains, 40.80 +/- 1.76 (mean +/- S.E.) nanomoles/min per mg protein, was almost twice the activity in neonatal strains, 22.40 +/- 3.02. This difference was significant at the 99.5% confidence level. Moreover, there was no overlap between the adult and neonatal activities. In contrast, adenosine kinase and purine nucleoside phosphorylase activities did not differ with the age of the donor.
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PMID:Adenosine deaminase activity in human diploid skin fibroblasts varies with the age of the donor. 10 69

Four Bovidae cell lines (BEK-1, MDBK, Bu and EBTr) were characterized by means of enzymatic biochemical markers. Out of 15 enzymatic systems, 3--adenosine deaminase (Ada), phosphoglucomutase (Pgm) and nucleoside phosphorylase (Np)--were found to be polymorphic and quite suitable for biochemical identification of each cell line. The Bu cell line has shown a Np phenotypic pattern which could be distinctive of the Bison bison species.
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PMID:Isozyme characterization of cattle (Bos taurus) and American buffalo (Bison bison) cell cultures. 10 20

The immunodeficient state associated with adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) deficiency may result from the selective phosphorylation by thymus-derived lymphocytes of the ADA substrate deoxyadenosine and the PNP substrate deoxyguanosine, leading to the intracellular trapping of toxic deoxyribonucleoside triphosphates. Agents such as deoxycytidine might be able to favourably modify the immunodeficient state by inhibiting deoxyribonucleoside phosphorylation. Deficiencies of other nucleotide catabolic enzymes, if selectively expressed by lymphocytes, might also lead to immunodeficiency via nucleoside trapping in lymphoid tissues. Purine deoxyribonucleoside analogues, either alone or in combination with ADA inhibitors, may have value as lymphospecific antimetabolites.
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PMID:Deoxyribonucleoside toxicity in adenosine deaminase and purine nucleoside phosphorylase deficiency: implications for the development of new immunosuppressive agents. 11 60

A protein which specifically complexes with adenosine deaminase (complexing protein) has been purified to homogeneity from human plasma. This protein was compared with complexing protein isolated from human kidney. The two proteins produce electrophoretically different forms of high molecular weight adenosine deaminase when combined with the Mr = 36,000 enzyme monomer from erythrocytes. This difference may, at least in part, be due to the greater sialic acid content of complexing protein from plasma. By other criteria, including amino acid composition, total carbohydrate content, and subunit structure, the two proteins are quite similar. In addition, plasma complexing protein shows complete cross-reactivity with anti-kidney complexing protein serum. These results suggest that plasma and kidney complexing proteins are products of the same gene.
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PMID:Purification of an adenosine deaminase complexing protein from human plasma. 11 75


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