ENZYME CATALYZATION OF THE DEACYLATION OF N-4-ACYL DERIVATIVES OF 1-BETA-D-ARABINOFURANOSYLCYTOSINE IN THE MOUSE-LIVER MICROSOME

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (6) , 2250-2254
Abstract
Enzymatic hydrolysis of acylamide of N4-acyl-1-.beta.-D-arabinofuranosylcytosine [a potential antitumor agent] was studied. The highest enzyme activity among various homogenates from mouse tissues, as expressed by specific activity, was found in liver homogenate. More than 50% of the activity in the liver was found in the microsomal fraction. The hydrolysis products of N4-palmitoyl-1-.beta.-D-arabinofuranosylcytosine by microsomal enzyme were identified stoichiometrically as 1-.beta.-D-arabinofuranosylcytosine and palmitic acid. The microsomal enzyme showed an optimum pH at 9.0 in Tris-HCl buffer. The Km for N4-palmitoyl-1-.beta.-D-arabinofuranosylcytosine was 2.5 .times. 10-5 M. The enzyme did not require divalent cations for the reaction. Mn2+ and Co2+ at 1 mM strongly inhibited the reaction. The relative rates of hydrolysis of N4-palmitoyl-, N4-stearoyl-, N4-lauroyl-, N4-butyryl-, and N4-behenoyl-1-.beta.-D-arabinofuranosylcytosine were 100, 47.6, 31.3, 15.9, and 9.1, respectively. The enzyme might play an important role in the formation of 1-.beta.-D-arabinofuranosylcytosine from N4-acyl derivatives of 1-.beta.-D-arabinofuranosylcytosine.