Phosphoribosyl transferase

Hypoxanthme-guanine-xanthiiie phosphoribosyl transferase Dock 88... 

Guanine Phosphoribosyl Transferase. Guanine phosphoribosyl transferase (GPRT) is one of the enzymes of the purine salvage pathway, which is needed by protozoa because they lack the ability to synthesize purine nucleotides. 

Two phosphoribosyl transferases then convert adenine to AMP and hypoxanthine and guanine to IMP or GMP (Figure 34-4). A second salvage mechanism involves phosphoryl transfer from ATP to a purine ri-bonucleoside (PuR) ... 

Chang H-K, GJ Zylstra (1999) Role of quinolinate phosphoribosyl transferase in degradation of phthalate by Burkholderia cepacia DBOl. J Bacteriol 181 3069-3075. 

Wang K, K Conn, G Lazarovits (2006) Involvement of quinolinate phosphoribosyl transferase in promotion of potato growth by a Burkholderia strain. Appl Environ Microbiol 72 760-768. 

J3. Jolly, D. J., Okayama, H Berg, P., Esty, A. C., Filpula, D Bohlen, P., Johnson, G. G., Shively, J. E., Hunkapillar, T., and Friedmann, T., Isolation and characterization of a full-length expressible cDNA for human hypoxanthine phosphoribosyl-transferase. Proc. Natl. Acad. Sci. U.S.A. 80,477-481 (1983). 

The answer is c. (Katzung, p 933.) Resistance to thioguanine occurs because of an increase in alkaline phosphatase and a decrease in hypoxanthine-guanine phosphoribosyl transferase. These enzymes are responsible, respectively, for the increase in dephosphorylation of thiopurine nucleotide and the conversion of thioguanine to its active form, 6-thioinosinic acid. 

Wu, C. L. and Melton, D. W. Production of a model for Lesch-Nyhan syndrome in hypoxanthine phosphoribosyl-transferase-deficient mice. Nat. Genet. 3 235-240,1993. 

There was no increase in mutation frequency at the hypoxanthine-guanine phosphoribosyl transferase gene locus in the presence or absence of S9 (Bootman et al. 1988b), and results were negative in a DNA repair assay with E. coli (Hodson-Walker and May 1988). 

PRTase - phosphoribosyl transferase ODCase - OMP decarboxylase OMP - orotidine 5 -phosphate... 

DNA = Deoxyribonucleic acid HGPRT = hypoxanthine-guanine phosphoribosyl transferase RNA = Ribonucleic acid -= negative result + = positive result (+) = weakly positive result... 

Brimer PA, Tan EL, Hsie AW. 1981. Effect of metabolic activation on the mutagenicity and cytotoxicity of ethylene dibromide in the Chinese hamster ovary hypoxanthine guanine phosphoribosyl transferase [Abstract]. Environ Mutagen 3 317-318. 

Histidine is a low molecular weight chelator considered to be important for the chelation of Ni (Kerkeb and Kramer, 2003). Its synthesis is limited by the enzyme ATP phosphoribosyl transferase, APRT. Transgenic A. thaliana plants over-expressing tHisG (a bacterial APRT) developed increased histidine levels and resulted in an enhanced Ni tolerance without affecting Ni accumulation (Wycisk et al., 2004). 

Fig. 13.1 Pathways of thiopurine metabolism. The positions of two polymorphically expressed enzymes, TPMT (thiopurine methyl transferase) and ITPA (inosine triphosphate pyrophosphatase), are shown. HGPRT, hypoxanthine guanine phosphoribosyl transferase 6-TIDP, 6-thioi-nosine diphosphate 6-TIMP, 6-thioinosine monophosphate 6-TITP, 6-thio inosine trinophosphate...

Fig. 14.2 Scheme of thiopurine drug metabolism. HPRT, hypoxanthine phosphoribosyl transferase 6-MMP, 6-methylmercaptopurine 6-TGN, 6-thioguanine nucleotides 6-TIMP, 6-thiosine monophosphate TPMT, thiopurine methyltransferase XO, xanthine oxidase... 

Most cases of hyperuricemia are due to disturbed uric acid excretion via the kidneys (1). A high-purine diet (e.g., meat) may also have unfavorable effects (2). A rare hereditary disease, Lesch-Nyhan syndrome, results from a defect in hypoxanthine phosphoribosyl-transferase (A, enzyme [1]). The impaired recycling of the purine bases caused by this leads to hyperuricemia and severe neurological disorders. 

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