Xanthine oxidase and adenosine deaminase in commercial bovine spleen phosphodiesterase preparations.

Commercial bovine spleen phosphodiesterase preparations contain xanthine oxidase activity; the xanthine oxidase in such preparations mediates the oxidation of a pteridine derivative as well as a standard purine substrate (hypoxanthine). The xanthine oxidase activity in the phosphodiesterase preparations is inhibited strongly by allopurinol (4-hydroxypyrazolo(3,4-d) pyrimidine). The reported ability of phosphodiesterase preparations to catalyze the deamination of adenosine derivatives appears to be due to contamination with a conventional adenosine deaminase in view of the observations that this activity is inhibited by an established inhibitor of adenosine deaminase and that the relative rates of deamination of N¹-methyladenosine and adenosine are similar with both the phosphodiesterase preparation and calf intestine adenosine deaminase.