Sensitivity of some arabinosylcytosine derivatives to enzymatic deamination by cytidine deaminase from mouse kidney

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 N4-acetyl-, tri-O-acetyl-, tetraacetyl derivatives and of cyclocytidine. The deamination of the anhydro derivative III to the corresponding uracil derivative IV proceeds significantly slower than that of arabinosylcytosine, and comparably to that of cyclocytidine. The deamination of the 5'-halogeno derivatives Ia, Ib and II proceeds via the anhydro derivative III to IV. Some of the known arabinosylcytosine derivatives, cyclocytidine, N4-acetyl-, tetraacetyl- and tri-O-acetyl derivatives, show a resistance to enzymatic deamination. Different nucleoside analogs are tested as inhibitors of deaminase; only 2-β-D-ribofuranosyl-1,2,4-triazol-3-one possesses some activity.