Adenosine deaminase specific

The antiviral state induced by different types of IFNs is mediated by various IFN-induced proteins. The best-known antiviral effectors produced as a result of IFN cascade induction are shown in Table 2. They include 2 -5 oligoadenylate synthetase (2 -5 OAS), double-stranded RNA activated protein kinase (PKR), and myxovirus (Mx) proteins. Additional effectors include RNA-specific adenosine deaminase 1 (ADARl), the 20-kDa ISG product (ISG20), ISG54 and ISG56, and IFN-stimulated micro RNAs (Pedersen et al. 2007). 

The importance of adenosine deaminase in the duration and intensity of sleep in humans has been noted recently (Retey et al. 2005). Animal studies suggest that sleep needs are genetically controlled, and this also seems to apply in humans. Probably, a genetic variant of adenosine deaminase, which is associated with the reduced metabolism of adenosine to inosine, specifically enhances deep sleep and slow wave activity during sleep. Thus low activity of the catabolic enzyme for adenosine results in elevated adenosine, and deep sleep. In contrast, insomnia patients could have a distinct polymorphism of more active adenosine deaminase resulting in less adenosine accumulation, insomnia, and a low threshold for anxiety. This could also explain interindividual differences in anxiety symptoms after caffeine intake in healthy volunteers. This could affect the EEG during sleep and wakefulness in a non-state-specific manner. 

Wolf, J., Gerber, A.P., and Keller, W. (2002) tadA, an essential tRNA-specific adenosine deaminase from Escherichia coli. EMBO J. 21(14), 3841-3851. 

Adenosine aminohydrolase (adenosine deaminase) is found in all types of cells and is apparently an important catabolic enzyme for the regulation of cellular metabolism. It has been isolated from a number of sources and the substrate specificities of the various enzymes are similar, since a low degree of specificity R... 

Chottiner EG, Gribbin TE, Ginsburg D, Mitchell BS. Erythrocyte-specific overproduction of adenosine deaminase molecular genetic studies. Prog Clin Biol Res 1989 319 55-64 discussion 65-8. 

Purine nucleotide catabolism is outlined in Figure 15.12. There is some variation in the specific pathways used by different organisms or tissues to degrade AMP. In muscle, for example, AMP is initially converted to IMP by AMP deaminase (also referred to as adenylate aminohydrolase). IMP is subsequently hydrolyzed to inosine by 5 -nucleotidase. In most tissues, however, AMP is hydrolyzed by 5 -nucleotidase to form adenosine. Adenosine is then deaminated by adenosine deaminase (also called adenosine aminohydrolase) to form inosine. 

Leucine aminopeptidase is interesting in that its active site contains two zinc atoms which together bind and activate the water molecule [74]. Despite this enzyme containing a dinuclear metal center at its active site, its mechanism, and specifically its mode of proton transfers reactions, appear to follow the general theme established by thermolysin and carboxypeptidase Adenosine deaminase and other members of the family of nucleoside and nucleotide deaminases utilize zinc-bound water as the catalytic nucleophile to displace ammonia from the 6-position of purines or the 4-position of pyrimidines and in all cases display inverse solvent deuterium isotope effects ranging from 0.3 to 0.8 on fec/Kni [75-80]. These effects are reminiscent of those observed for metallopro-teases and have their origins, like those of the proteases, in fractionation factors for the protons of the bound water that are less than one. 

The specificity of ethirimol towards mildews may be related to the presence in mildews of an unusual form of the enzyme adenosine deaminase, which is absent from other organisms. Differences in either the amount of this enzyme present or its sensitivity to ethirimol may explain why fungicide activity differs between mildew species (Hollomon, 1979b, Hollomon and Chamberlain, 1981). 

In addition to its role as a messenger, adenosine has other strong effects on cells. This compound is toxic to cells in culture even at a concentration as low as 10 5 M, probably through its interference with pyrimidine biosynthesis in cells30. This toxicity is manifested only in a specifically designed system since many sera, e.g., calf or human, that are used to grow cells contain adenosine deaminase, an enzyme that immediately detox-... 

Few detailed studies have been done on the purine salvage enzymes of procyclic African trypanosomes. Tb. gambiense has high levels of guanine deaminase and lacks adenine and adenosine deaminase activities (8). Tb. brucei, T.b. gambiense and T.b. rhodesiense convert allopurinol into aminopyrazolopyrimidine nucleotides and incorporates these into RNA (49). This indicates that HPRTase, succino-AMP synthetase, and succino-AMP lyase are present. At least three nucleoside cleavage activities are present (Berens, unpublished results) two are hydrolases, of which one is specific for purine ribonucleosides and the other is specific for purine deoxyribonucleosides. The third nucleoside cleavage activity is a methylthioadenosine/adenosine phosphorylase. The adenosine kinase is similar to that of L. donovani (Berens, unpublished results). 

T.b. gambiense bloodstream forms have APRTase, HGPRTase, adenosine kinase and adenylosuccinate synthetase but lack adenosine deaminase. Two phosphorylase activities have been described for the bloodstream forms of T.b. brucei (42,50). One catalyzes the reversible phosphorolysis of adenosine, inosine and guanosine and the other is specific for adenosine and methylthioadenosine. Guanine deaminase is present whereas both adenosine and adenine deaminase are absent (8). Similar results have been reported for T. congolense (51). T. vivax is unique among the other trypanosomes in that it has an adenine deaminase (51). 

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