What is the role of DNA synthesis in human RBC
Uma maheswari M, Asokkumar K, Sivashanmugam AT, Remyaraju A, Subhadradevi V, Ravi TK. In vitro xanthine oxidase inhibitory activity of the fractions of Erythrina stricta roxb. J Ethnopharmacol 2009;124:646-8.
Effects of Hypoxanthine–Xanthine Oxidase on Ca2+ …
Pathways of mammalian purine nucleotide synthesis. The pathway is shown schematically from the top as well as the central role of IMP in nucleotide interrelations. Salvage of purine bases is catalysed by hypoxanthine guanine phosphoribosyltransferase (HGPRT) and adenine phosphoribosyltransferase (APRT). Other abbreviations include: ASL, adenylosuccinate lyase; AMPDA, adenylate deaminase; ADA, adenosine deaminase; PNP, purine nucleoside phosphorylase; XO, xanthine oxidase; and PPi, inorganic pyrophosphate.
T1 - Xanthine oxidase-derived extracellular superoxide anions stimulate activator protein 1 activity and hypertrophy in human vascular smooth muscle via c-Jun N-terminal kinase and p38 mitogen-activated protein kinases
Human xanthine oxidoreductase (XOR ..
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18/11/2014 · Xanthine oxidase (XO) is an important ..
Malaria parasites, unable to synthesize purine de novo, use host-derived hypoxanthine preferentially as purine source. In a previous study (1990. J. Biol. Chem. 265:6562-6568), we noted that xanthine oxidase rapidly and completely depleted hypoxanthine in human erythrocytes, not by crossing the erythrocyte membrane, but rather by creating a concentration gradient which facilitated hypoxanthine efflux. We therefore investigated the ability of xanthine oxidase to inhibit growth of FCR-3, a chloroquine-resistant strain of Plasmodium falciparum in human erythrocytes in vitro. Parasites were cultured in human group O+ erythrocytes in medium supplemented, as required, with xanthine oxidase or chloroquine. Parasite viability was assessed by uptake of radiolabeled glycine and adenosine triphosphate-derived purine into protein and nucleic acid, respectively, by nucleic acid accumulation, by L-lactate production, and by microscopic appearance. On average, a 90% inhibition of growth was observed after 72 h of incubation in 20 mU/ml xanthine oxidase. Inhibition was notably greater than that exerted by 10(-7) M chloroquine (less than 10%) over a comparable period. The IC50 for xanthine oxidase was estimated at 0.2 mU/ml, compared to 1.5 x 10(-7) M for chloroquine. Inhibition was completely reversed by excess hypoxanthine, but was unaffected by oxygen radical scavengers, including superoxide dismutase and catalase. The data confirms that a supply of host-derived hypoxanthine is critical for nucleic acid synthesis in P. falciparum, and that depletion of erythrocyte hypoxanthine pools of chloroquine-resistant malaria infection in humans. of chloroquine-resistant malaria infection in humans.
Xanthine oxidoreductase (XOR ..
In primates, the end product of purine nucleotide catabolism is uric acid, which is excreted as such. Pathways leading to uric acid vary considerably in different tissues and cells. Most of the reactions involved are shown in Figure 4. Note, for example, that AMP degradation can begin either with deamination, to yield IMP, or with hydrolysis, to yield adenosine. In mammals, the deamination pathway is particularly active in muscle tissue. Both pathways lead to the nucleoside inosine, which is cleaved by inorganic phosphate and purine nucleoside phosphorylase , yielding ribose 1-phosphate and hypoxanthine. Hypoxanthine is oxidized by the versatile molybdenum- and iron-containing enzyme, xanthine oxidase , to xanthine, which is also produced by guanine nucleotide catabolism. Xanthine is also acted on by xanthine oxidase, to give uric acid. As noted, the process ends here in primates. However, most animals further degrade uric acid to allantoin and then to allantoic acid. Some fishes excrete allantoic acid, but most aquatic animals further catabolize allantoic acid to urea and, in the case of marine invertebrates, to ammonia. These latter pathways are summarized in Figure 5.