The phosphorolysis of nucleosides by rabbit bone marrow.

It has been reported that the capacity of rabbit bone marrow to carry out the synthesis de novo of purine ribonucleotides is quite low, and that this tissue requires preformed purine derivatives supplied by the liver (1, 2). Presumably, the salvage enzymes, including nucleoside phosphorylases (3),. participate in the reutilization of the preformed derivatives. So far, only pyrimidine nucleoside phosphorylases of rabbit and human bone marrow have been described (4,5). It was very probable, then, in view of their wide distribution in other tissues (6)) that purine nucleoside phosphorylases would also be present in bone marrow cells. This investigation resulted in the isolation of a nucleoside phosphorylase that appears to be highly specific for guanosine and deoxyguanosine. In this respect, the enzyme is unlike the purine nucleoside phosphorylases isolated from liver (7)) erythrocytes (8), and brain (9).