Recycling of alpha-D-ribose 1-phosphate for nucleoside interconversion.
Mobilization of the ribose moiety and of the amino group of guanosine may be realized in rat liver extract by the concerted action of purine nucleoside phosphorylase and guanase. Ribose 1-phosphate formed from guanosine through the action of purine nucleoside phosphorylase acts as ribose donor in the synthesis of xanthosine catalyzed by the same enzyme. The presence of guanase, which irreversibly converts guanine to xanthine, affects the overall process of guanosine transformation. As a result of this purine pathway, guanosine is converted into xanthosine, thus overcoming the lack of guanosine deaminase in mammals. Furthermore, in rat liver extract the activated ribose moiety stemming from the catabolism of purine nucleosides can be transferred to uracil and, in the presence of ATP, used for the synthesis of pyrimidine nucleotides; therefore, purine nucleosides can act as ribose donors for the salvage of pyrimidine bases.
Giorgelli
F
F
Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy.
Bottai
C
C
Mascia
L
L
Scolozzi
C
C
Camici
M
M
Ipata
P L
PL
D000818:Animals; D006148:Guanine Deaminase / Q000378:metabolism; D006151:Guanosine / Q000378:metabolism; D011684:Purine Nucleosides / Q000378:metabolism*; D011683:Purine-Nucleoside Phosphorylase / Q000378:metabolism*; D011742:Pyrimidine Nucleotides / Q000096:biosynthesis; D051381:Rats; D012263:Ribonucleosides / Q000378:metabolism; D012266:Ribose / Q000378:metabolism; D012267:Ribosemonophosphates / Q000378:metabolism*; D015219:Substrate Cycling; D014020:Tissue Extracts / Q000378:metabolism; D014500:Uracil Nucleotides / Q000378:metabolism; D014970:Xanthines
D011684:Purine Nucleosides; D011742:Pyrimidine Nucleotides; D012263:Ribonucleosides; D012267:Ribosemonophosphates; D014020:Tissue Extracts; D014500:Uracil Nucleotides; D014970:Xanthines; D006151:Guanosine; C031154:ribose 1-phosphate; D012266:Ribose; C005893:xanthosine; D011683:Purine-Nucleoside Phosphorylase; D006148:Guanine Deaminase