In vitro recycling of alpha-D-ribose 1-phosphate for the salvage of purine bases.
In this paper, we extend our previous observation on the mobilization of the ribose moiety from a purine nucleoside to a pyrimidine base, with subsequent pyrimidine nucleotides formation (Cappiello et al., Biochim. Biophys. Acta 1425 (1998) 273-281). The data show that, at least in vitro, also the reverse process is possible. In rat brain extracts, the activated ribose, stemming from uridine as ribose 1-phosphate, can be used to salvage adenine and hypoxanthine to their respective nucleotides. Since the salvage of purine bases is a 5-phosphoribosyl 1-pyrophosphate-dependent process, catalyzed by adenine phosphoribosyltransferase and hypoxanthine guanine phosphoribosyltransferase, our results imply that Rib-1P must be transformed into 5-phosphoribosyl 1-pyrophosphate, via the successive action of phosphopentomutase and 5-phosphoribosyl 1-pyrophosphate synthetase; and,in fact, no adenosine could be found as an intermediate when rat brain extracts were incubated with adenine, Rib-1P and ATP, showing that adenine salvage does not imply adenine ribosylation, followed by adenosine phosphorylation. Taken together with our previous results on the Rib-1P-dependent salvage of pyrimidine nucleotides, our results give a clear picture of the in vitro Rib-1P recycling, for both purine and pyrimidine salvage.
Mascia
L
L
Department of Physiology and Biochemistry, University of Pisa, Via S. Maria 55, 56126, Pisa, Italy.
Cappiello
M
M
Cherri
S
S
Ipata
P L
PL
D000818:Animals; D001921:Brain / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D010754:Phosphoribosyl Pyrophosphate / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism; D011687:Purines / Q000378:metabolism*; D011742:Pyrimidine Nucleotides / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012267:Ribosemonophosphates / Q000378:metabolism*; D015219:Substrate Cycling
D011687:Purines; D011742:Pyrimidine Nucleotides; D012267:Ribosemonophosphates; C031154:ribose 1-phosphate; D010754:Phosphoribosyl Pyrophosphate; D010770:Phosphotransferases; C022375:phosphopentomutase