Resistance of Cyclocytidine to Cytidine Deaminase

Deamination of cytidine derivatives especially of cyclocytidine by mouse kidney cytidine deaminase was examined. Cyclocytidine was not deaminated at either pH6.5 or pH7.3 by the enzyme. Furthermore, cyclocytidine did not inhibit the deamination of aracytidine and ([I]/[S])0.5 value for cyclocytidine was over 100. As a result, cyclocytidine is found to be markedly active compound with resistance against cytidine deaminase.