Abstract Enzymatic deamination of derivatives of arabinosylcytosine by partially purified cytidine deaminase isolated from mouse kidney is studied. The rate of deamination of 5'- chloroarabinosylcytosine (Ia), 5'-bromoarabinosylcytosine (Ib), 5'-chlorocyclocytidine (II), and 2', 5'-anhydroarabinosylcytosine (III) is compared with that of arabinosylcytosine, of its N 4-acetyl-, tri-O-acetyl-, tetraacetyl derivatives and of cyclocytidine. The deamination of the ...