Xanthine ribosyl

Stereochemical Configuration. Deamination by means of nitrous acid transforms adenosine into inosine (ribosyl-hypoxanthine), and guanosine into xanthosine (ribosyl-xanthine). These four purine nucleosides are hydrolyzed rapidly, and with equal ease, by dilute mineral acids. They are also all hydrolyzed by the same enzyme, so it is reasonable to presume that they are similarly constituted as regards the stereochemical disposition at the sugar-base link. Whether this is of the a- or i8-configuration is still unknown. 

We report here on the mechanism of DNA strand breakage and poly(ADP-ribosyl)ation by AO in comparison to the methylating agent N-methyl-N -nitro-N-nitrosoguanidine (MNNG) in promotable JB6 clone 41 cells. We also summarize first results on the identity of the nuclear proteins which serve as poly(ADP-ribose) acceptors in response to AO. We chose xanthine/xanthine oxidase (X/XO) as a source of extracellular AO because it produces a mixture of superoxide and H2O2 which resembles the oxidants released by macrophages and mouse epidermal cells JB6 because promotable (clone 41) and non-promotable (clone 30) variants are available (9). 

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