There is an iron-dependent activity in the venom of Crotalus atrox which
appears to hydrolyze the N-glycosidic sugar-base bond of pyrimidine and purine nucleotides.
Maximal activation of this activity occurred at 1.0 mmol/1 and 0.8 mmol/1 FeCl(3) for cytidine
diphosphate (CDP) and ADP substrates, respectively. The release of free base affects the
background values of control experiments carried out during nucleotide-labelled assays of
ribonucleotide reductase which require the conversion of nucleotides to nucleosides by snake
venom treatment. When the reductase is examined in intact cells, a situation closely resembling
normal physiological conditions for the enzyme, FeCl(3) was found to be an inhibitor of
ADP reductions and varied from a mild stimulator to a significant inhibitor of CDP reductions
depending upon FeCl(3) concentration. Possible explanations for previously observed
variability in ribonucleotide reductase activity in the presence of iron are suggested.
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