Inhibition of 5'-deoxy-5-flourouridine phospholysis by acyclopyrimidinenucleosides in intestinal tissue homogenates

Article abstract of DOI:10.1248/bpb.18.172

This study examined the inhibitory effect of acyclopyrimidinenucleosides on 5'-deoxy-5-fluorouridine (5'-DFUR) phosphorolysis in intestinal tissue derived from rabbit, rat, mouse, and human. 5-Bromoacyclouridine, 5-fluoroacyclouridine, acyclouridine, and 5-nitroacyclouridine showed little or only moderate effect, but acyclothymidine [5-methyl-1-(2'-hydroxyethoxymethyl)uracil] showed strong inhibitory effect on 5'-DFUR phosphorolysis in intestinal tissue homogenates derived from human. In the absence of inhibitor (acyclothymidine), the V(max) of 5'-DFUR phosphorolysis was 2.66 μmol/min and the K(m) was 0.57 mM in human intestinal homogenates. The V(max) was unaltered by increased inhibitor concentration. The maximal inhibitory effect of acyclothymidine on 5'-DFUR phosphorolysis in rat homogenates was over 90%. The K(i)/K(m) was 0.63 in human, 2.14 in rabbit, 1.09 x 10^-2 in rat, and 1.71 x 10^-2 in mouse. These data show that acyclothymidine is a competitive inhibitor of 5'-DFUR phosphorolysis, and that it can inhibit not only uridine phosphorylase but also thymidine phosphorylase.

Full text of DOI:10.1248/bpb.18.172

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