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Purine nucleoside hydrolases

M.-C. Ho, W. Shi, A. Rinaldo-Matthis, P. C. Tyler, G. B. Evans, K. Clinch, S. C. Almo, and V. L. Schramm, Four generations of transition-state analogues for human purine nucleoside hydrolase, Proc. Natl. Acad. Sci. USA, 107 (2010) 4805 -812. [Pg.294]

Figure 5.29 Isoenzyme-specific inhibitors of purine nucleoside hydrolases. Figure 5.29 Isoenzyme-specific inhibitors of purine nucleoside hydrolases.
Schmidt, G., Walter, R. D. and Koni, E. (1975) A purine nucleoside hydrolase from Trypanosoma gambiense, purification and properties. Tropenmed. Parasitol. 26 19-26. [Pg.114]

Thie enzyme [EC 3.2.2.1], also known as inosine-uridine preferring nucleoside hydrolase and lU-nucleoside hydrolase, catalyzes the hydrolysis of an A-o-ribosylpurine to produce a purine and D-ribose. [Pg.589]

The abnormal T- and B-cell functions in patients with SCID are the result of ADA dehciency. The ADA gene has been mapped to chromosome 20q.l3, and a number of point and deletion mutations have been identihed in SCID patients [5-7]. ADA catalyses the irreversible deamination of adenosine and 2 -deoxyadenosine to inosine and 2 -deoxyi-nosine as a part of purine nucleoside metabolism. Adenosine and deoxyadeno-sine are suicide inachvators of S-adenosyl-homocysteine (SAH) hydrolase, and lead indirectly to intracellular accumulation of SAH, which is a potent inhibitor of methy-lation reactions. Cellular methylation function is essential for detoxihcation of adenosine and deoxyadenosine. As a result ADA dehciency leads to accumulation to... [Pg.246]

Trypanosomes and other parasitic protozoa are unable to synthesize purines and must obtain them from their hosts using salvage pathway. Selective inhibition of their HGPRT or of nucleoside hydrolases, which are absent from mammalian cells, are goals of drug development.3273 1 ... [Pg.1457]

Nucleoside hydrolase has been proposed to participate in purine salvage in the trypanosome Crithidia fasciculata. The enzyme hydrolyses the N-glycosidic linkage of the naturally occurring purine and pyrimidine nucleosides. A geometric model of the transition state for nucleoside hydrolase for the reaction (Horenstein et al., 1991)... [Pg.283]

Evolutionary pressures have constrained pertussis toxin to a mechanism with significant nucleophile participation while RTA has evolved a catalytic strategy with an oxocarbenium ion intermediate that reacts quickly with nearby water molecules. By this logic, other ADP-ribosylating toxins, such as cholera and diphtheria toxins, would be expected to proceed through relatively synchronous transition states. Nucleoside hydrolases (enzymes that hydrolyze nucleosides to ribose and a purine or pyrimidine base) could use mechanisms with oxocarbenium ion intermediates, though the transition states characterized to date have been A Dn (see below). [Pg.275]

Individual enzymes of purine salvage are similar to those of Leishmania. PRTase activities were found for adenine, hypoxanthine, and guanine in the three forms (43). As in Leishmania, there is also a separate xanthine PRTase. Nucleoside kinase activities were found for adenosine, inosine, and guanosine (43), nucleoside hydrolase activities for inosine and guanosine and a nucleoside phosphorylase activity for adenosine. There are both nucleoside hydrolase and phosphorylase activities in epimastigotes (44,45). The adenylosuccinate synthetase and adenylosuccinate lyase are essentially identical to those found in L. donovani (46). [Pg.97]

Cui L, Rajasekariah GR, Martin SK. A nonspecific nucleoside hydrolase from Leishmania donovani Implications for purine salvage by the parasite. Gene 2001 280(1-2) 153-162. [Pg.152]

Outside the CNS (central nervous system), pyrrole Mannich bases have found utility in other therapeutic areas as well. The Mannich reaction between iminoibitol and 9-deazahypoxanthine took place at the C3 position to provide an A-pyrrolylmethyl substituted iminoribitol as an inhibitor of a purine-specific nucleoside hydrolase. In terms of regiochemistry, this particular Mannich reaction of 9-deazahypoxanthine behaved similarly to indole rather than to pyrrole. The resulting Mannich bases are potential treatment for parasitic infections. [Pg.27]

Camellia (Thea) sinensis (tea) and Cqffea arabica (coffee) plants. Caffeine was formed rapidly by extracts of green coffee berries, but little by more mature ones, and not at all by seedlings. Biosynthesis of caffein proceeds from 7-methylxanthosine in the presence of an active purine nucleoside phosphorylase or 7-methyl-A -nucleoside hydrolase. Methionine and 5-adenosylmethionine serve as precursors for the methyl groups of purine alkaloids. These act in the presence of methyltransferases on 7-methylxanthine (38) and theobromine (31) to produce caffeine. A pathway for the origin of these compounds in coffee and tea plants has been proposed (Suzuki et al., 1992 Waller and Dermer, 1981) (Fig. 37.10). [Pg.702]

It was previously reported that L. donovani had high levels of nucleoside hydrolase activities toward all the common purine nucleosides except adenosine. It was clear that if the phospho-rylase-kinase pathway was the only route of purine salvage in trichomonas the presence of such hydrolases would be difficult to explain. Figure 3 shows the nucleoside hydrolase levels of leish-mania and trichomonas. With leishmania, the levels are high with... [Pg.216]

Several nucleoside hydrolases have been described. A hydrolase purified from baker s yeast (79) has been found which specifically degrades uridine to uracil and n-ribose. Another nucleoside hydrolase also purified from yeast splits guanoane, adenosine, inosine, xanthosine, nicotinamide riboside, and a group of synthetic unnatural riborides. A highly specific uridine hydrolase is found in yeast, and a nucleoride hydrolase has been described in Lactobacillus pentosus which degrades both purine and pyrimidine nucleosides (74)- A nonspecific hydrolase as well as a i cific inosine hydrolase have been purified from fish muscle (76). The spores of BaciUus eereus contain a heat-stable hydrolase which can cleave adenosine and inosine (76, 77). Finally, a riboside hydrolase of broad spedfidty which attacks only 9-ribofuranosides has been purified from extracts of Ladobacil-lus delbrueckii (72, 78). [Pg.471]

Nucleosidase—a hydrolase that breaks nucleosides into a purine or pyrimidine and ribose. [Pg.77]

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). [Pg.98]

Bios5mthetic pathways of naturally occurring cytokinins are illustrated in Fig. 29.5. The first step of cytokinin biosynthesis is the formation of A -(A -isopentenyl) adenine nucleotides catalyzed by adenylate isopentenyltransferase (EC 2.5.1.27). In higher plants, A -(A -isopentenyl)adenine riboside 5 -triphosphate or A -(A -isopentenyl)adenine riboside 5 -diphosphate are formed preferentially. In Arabidopsis, A -(A -isopentenyl)adenine nucleotides are converted into fraws-zeatin nucleotides by cytochrome P450 monooxygenases. Bioactive cytokinins are base forms. Cytokinin nucleotides are converted to nucleobases by 5 -nucleotidase and nucleosidase as shown in the conventional purine nucleotide catabolism pathway. However, a novel enzyme, cytokinin nucleoside 5 -monophosphate phosphoribo-hydrolase, named LOG, has recently been identified. Therefore, it is likely that at least two pathways convert inactive nucleotide forms of cytokinin to the active freebase forms that occur in plants [27, 42]. The reverse reactions, the conversion of the active to inactive structures, seem to be catalyzed by adenine phosphoiibosyl-transferase [43] and/or adenosine kinase [44]. In addition, biosynthesis of c/s-zeatin from tRNAs in plants has been demonstrated using Arabidopsis mutants with defective tRNA isopentenyltransferases [45]. [Pg.963]

Fig. 23.1. Pyrimidine pathways Pathways for the de novo synthesis, interconversion, and breakdown of pyrimidine ribonucleotides, indicating their metabolic importance as the essential precursors of the pyrimidine sugars and, with purines, of DNA and RNA. Note that in contrast to purines salvage takes place at the nucleoside not the base level in human cells and pyrimidine metabolism normally lacks any detectable end-product. The importance of this network is highlighted by the variety of clinical symptoms associated with the possible enzyme defects indicated. 23.10, Uridine monophosphate synthase (UMPS), 23.11a, uridine monophosphate hydrolase 1 (UMPHl), 23.12, thymidine phosphorylase (TP), 23.13, dihydropyrimidine dehydrogenase (DPD), 23.14, dihydropyrimidine amidohydrolase (DHP), 23.15, y -ureidopropionase (UP) (23.11b, UMPH superactivity specific to fibroblasts is not shown). CP, carbamoyl phosphate. The pathological metabolites used as specific markers in differential diagnosis are highlighted... Fig. 23.1. Pyrimidine pathways Pathways for the de novo synthesis, interconversion, and breakdown of pyrimidine ribonucleotides, indicating their metabolic importance as the essential precursors of the pyrimidine sugars and, with purines, of DNA and RNA. Note that in contrast to purines salvage takes place at the nucleoside not the base level in human cells and pyrimidine metabolism normally lacks any detectable end-product. The importance of this network is highlighted by the variety of clinical symptoms associated with the possible enzyme defects indicated. 23.10, Uridine monophosphate synthase (UMPS), 23.11a, uridine monophosphate hydrolase 1 (UMPHl), 23.12, thymidine phosphorylase (TP), 23.13, dihydropyrimidine dehydrogenase (DPD), 23.14, dihydropyrimidine amidohydrolase (DHP), 23.15, y -ureidopropionase (UP) (23.11b, UMPH superactivity specific to fibroblasts is not shown). CP, carbamoyl phosphate. The pathological metabolites used as specific markers in differential diagnosis are highlighted...
Although AdoHcy hydrolase is not found in bacteria, AdoHcy is cleaved irreversibly to adenine and S-rlbosyl-L-homocystelne by AdoHcy nucleosidase ". This enzyme has been partially purified from E, aoliy and found to catalyze also the hydrolysis of 5 -methy1-thioadenosine to adenine and methylthiorlbose. The enzyme is inactive towards AdoMet and a variety of other purine and pyrimidine nucleosides. The specific activity of AdoHcy nucleosidase is 1000 x greater than that of AdoHcy hydrolase emphasizing the need to remove AdoHcy, a potent inhibitor of reactions which utilize AdoMet as a substrate. [Pg.72]


See other pages where Purine nucleoside hydrolases is mentioned: [Pg.90]    [Pg.90]    [Pg.244]    [Pg.438]    [Pg.423]    [Pg.232]    [Pg.240]    [Pg.276]    [Pg.91]    [Pg.391]    [Pg.144]    [Pg.147]    [Pg.122]    [Pg.185]    [Pg.688]    [Pg.638]    [Pg.122]    [Pg.100]   
See also in sourсe #XX -- [ Pg.217 ]




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Nucleoside hydrolase

Purine nucleosides

Purine specific nucleoside hydrolase

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