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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)

Total adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) activities were measured in cell samples from 13 cases of de novo acute leukemia and from three cases of chronic myeloid leukemia in blast crisis (CMLBC). These cases could be separated into lymphoid and nonlymphoid types on the basis of enzyme activity, with two misclassifications. However, PNP activity added little or no discriminatory information. Analysis for expression of the various molecular weight (mol wt) ADA isozymes, ADA1 (40 Kd) and ADA2 (110 Kd), revealed that ADA2 was expressed exclusively in nonlymphoid cells whereas ADA1 was found in both lymphoid and nonlymphoid cell types. Identification of ADA2 divided these leukemia cases into lymphoid and nonlymphoid types with no misclassifications (P = .0002; Fisher's exact test). Acute nonlymphoblastic leukemia (ANLL) with a monocytic component tended to have a greater percentage of ADA2 than ANLL without a monocytic component. These studies suggest that ADA2 may be a novel biochemical marker for an immature nonlymphoid cell.
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PMID:Differential expression of adenosine deaminase isozymes in acute leukemia. 314 Sep 11

The adenosine deaminase gene frequencies were calculated in 405 subjects randomly chosen from the Bigouden district. A rather high frequency (0.0765 +/- 0.0093) was found for the ADA2 gene. The possible effect of Celtic influences is considered.
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PMID:Frequency of red cell adenosine deaminase phenotypes in a unique Breton community, the Bigoudens. 339 70

Extracts of liver and spleen were used to isolate opossum adenosine deaminase isoenzymes (ADA1 and ADA2) and to determine their activities with adenosine and 2'-deoxyadenosine as substrates. Km values (microM) for adenosine and 2'-deoxyadenosine, respectively, as substrates for partially purified opossum liver adenosine deaminase isoenzymes were ADA1: 57 +/- 7 vs. 26 +/- 4 and ADA2: 285 +/- 25 vs. 580 +/- 92. In crude spleen extract, ADA2 activity was stable at 56 degrees C during 40 min of incubation. ADA1 activity declined in a linear fashion under the above conditions with an apparent T1/2 of 80 min. Sephadex G-150 column chromatography of crude spleen extract showed the apparent molecular weight of the ADA activity not inhibited by (+/-)-EHNA (i.e. ADA2) to be 170 kDa; ADA activity fully inhibited by (+/-)-EHNA (i.e. ADA1) eluted in the fractions corresponding to a molecular weight of 35 kDa.
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PMID:Adenosine deaminase isoenzymes of the opossum Didelphis virginiana: initial chromatographic and kinetic studies. 759 90

Adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4; ADA) activity is widely distributed in human tissues and is highest in lymphoid tissues. Two ADA isozymes are known as ADA1 and ADA2. Human tissue extracts contained ADA1 predominantly. Meanwhile, ADA2 was the main component of serum ADA. ADA activity was significantly elevated in the sera from patients with hepatic diseases, hematological malignancies and infectious diseases. Serum concentrations of ADA1 were high in patients with acute leukemias, chronic myeloid blast crisis leukemia and acute liver injury. Serum ADA2 levels were raised in patients with adult T-cell leukemia, multiple myeloma (B-J type), infectious mononucleosis, rubella, acquired immunodeficiency syndrome, chronic hepatic diseases and tuberculosis. It is supposed that ADA1 is derived mainly from injured tissues or cells while ADA2 comes from stimulated T-cells.
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PMID:[Adenosine deaminase]. 760 76

To clarify the clinical significance of increased serum adenosine deaminase (ADA) activity, and its mechanisms in various liver diseases, ADA isoenzyme activities (ADA1 and ADA2) in serum and the peripheral blood mononuclear cells were studied. High serum ADA activities were found in patients with acute hepatitis, alcoholic hepatic fibrosis, chronic active hepatitis, liver cirrhosis, and hepatoma. The ADA2:ADA ratio was decreased in acute hepatitis, but was increased in chronic active hepatitis and liver cirrhosis. Clinically, ADA2 activity was correlated with serum gamma-globulin levels. In chronic active hepatitis, total ADA activities in the peripheral blood mononuclear cells were similar to those in controls. Furthermore, ADA2 activities after phytohemagglutinin (PHA) stimulation were significantly lower than those without PHA stimulation, although total ADA activities were increased after PHA stimulation. These findings suggest that serum ADA isoenzyme activities may be a new marker for liver disease, and that the increased serum ADA2 in chronic active hepatitis is unlikely to be the result of an increase in ADA2 production by activated peripheral blood mononuclear cells.
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PMID:Adenosine deaminase isoenzymes in liver disease. 842 31

In serum, the enzyme adenosine deaminase (ADA) is known to be divided into two isoenzymes, ADA1 and ADA2, which have different molecular weights and kinetic properties. The present study investigated ADA isoenzyme levels in the sera of patients infected with retroviruses associated with adult T-cell leukemia (ATL), human T-cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy (HAM), and AIDS, ADA isoenzyme activities were found to be significantly (P < 0.001) higher in the sera of patients with ATL, HAM, and AIDS than in the sera of healthy controls. In the case of the ADA subtypes in the sera of patients with ATL, ADA1 activity was significantly (P < 0.001) elevated in patients with the acute and lymphoma types of ATL compared with that in patients with the chronic and smoldering types of ATL. ADA2 activity was significantly elevated in the sera of patients with the acute, lymphoma, and chronic types of ATL (P < 0.001) compared with that in patients with smoldering ATL and HTLV-1 carriers. In the case of patients with human immunodeficiency virus type 1 (HIV-1) infection, ADA1 and ADA2 activities in the sera of patients with AIDS and HIV-1 antibody-positive individuals were significantly (P < 0.001) higher than those in the sera of HIV-1 antibody-negative individuals. A significant elevation in ADA2 activity was also seen in the sera of AIDS patients (P < 0.01) compared with that in the sera of HIV-1 antibody-positive individuals. These results suggest that the magnitude of elevation of ADA isoenzyme levels in serum correlates well with the clinical conditions of the patients with these diseases. Measurement of the activities of ADA isoenzymes may therefore provide an additional parameter for distinguishing the subtypes of ATL and may prove to be useful as prognostic and therapeutic monitors in diseases associated with HTLV-1 and HIV-1 infections.
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PMID:Adenosine deaminase isoenzyme levels in patients with human T-cell lymphotropic virus type 1 and human immunodeficiency virus type 1 infections. 854 45

Total adenosine deaminase (ADA) activity and its isozyme (ADA1 and ADA2) activities were measured in pleural effusions and serum samples from patients with tuberculosis and in those from patients with lung cancer as controls. To analyze the cellular source of ADA isozymes in tuberculous pleural effusions, ADA isozyme activities in CD2+ T lymphocytes purified from tuberculous pleural effusions and cultured human cell lines derived from hematopoietic tumors were measured. Tuberculous pleural effusions had a much higher ADA activity than cancerous effusions, and high ADA activity mainly originated from the increase in ADA2 activity. Further, total ADA activity in tuberculous pleural effusions decreased after antituberculosis treatment, because of the decrease in ADA2 activity. On the other hand, measurement of ADA and ADA isozyme activities in T lymphocytes purified from tuberculous pleural effusions and human hematopoietic cell lines showed dominant expression of ADA1 in total ADA activity. In conclusion, we found that ADA2 is a dominant component of tuberculous pleural effusions and that ADA1 is a major component of lymphoid cells. These results suggest that elevation of ADA activity in tuberculous pleural effusions does not always reflect the activation of cell-mediated immunity.
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PMID:Adenosine deaminase isozymes in tuberculous pleural effusion. 865 33

The activity of serum adenosine deaminase and its isoenzymes (ADA1 and ADA2) was measured in the sera of 55 patients with clinically diagnosed typhoid fever, 46 of whom were seropositive for Salmonella typhi infection. At presentation 95% of the serologically positive patients had increased serum adenosine deaminase activity. The increase in activity was greater than that of other frequently measured enzymes. Isoenzyme ADA2 accounted for 84% of the activity, indicating a monocyte/macrophage origin. Results show that in patients with typhoid fever, serum adenosine deaminase, particularly its isoenzyme ADA2, may be regarded as a marker for monocyte/macrophage activation and could be valuable in diagnosis.
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PMID:Adenosine deaminase isoenzymes in typhoid fever. 883 48

The isoenzymes ADA1 and ADA2 of the enzyme adenosine deaminase (ADA 3.5.4.4) deaminate mainly two nucleotides: adenosine and 2'-deoxyadenosine, molecules with many effects on human cells. Thus, the ADA1 and ADA2 in human cells are of extreme importance. Biochemical and biological properties of the isoenzymes ADA1 and ADA2 as well as their usefulness in diagnostic of many diseases were described.
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PMID:[Adenosine deaminase: isoenzymes ADA1 and ADA2]. 952 70

Regarding homeostatic mechanisms in the enzyme (isoenzymes) and substrate system we show through a simulation model obtained by STELLA II software that: (i) a pair of isoenzymes (Is1 and Is2) that have different affinity for the substrate (Is2 affinity < Is1 affinity), can constitute an efficient homeostatic mechanism: by varying the relative concentration of the isoenzymes in the system, the levels of the substrate can be controlled; (ii) the isoenzymes ADA1 and ADA2 of adenosine deaminase (ADA) that have different affinity for the substrate 2'deoxyadenosine (ADA2 has very weak affinity for 2'deoxyadenosine) constitute, inside human Monocytes-Macrophages, a homeostatic mechanism that assures an up-regulation of 2'deoxyadenosine and a down-regulation of a second substrate (adenosine) for which the affinity of the two isoenzymes is similar.
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PMID:Enzymes (isoenzyme system) as homeostatic mechanisms the isoenzyme (ADA2) of adenosine deaminase of human monocytes-macrophages as a regulator of the 2'deoxyadenosine. 981 88


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