3-Cyano-2,6-dihydroxypyridine (CNDP), a new potent inhibitor of dihydrouracil dehydrogenase.

K Tatsumi, T Yamauchi, K Kiyono, K Kishi, Y Yanagihara, T Imaoka, T Kawaguchi, M Kubo

Fujii Memorial Research Institute, Otsuka Pharmaceutical Co., Ltd., Shiga.

Journal of biochemistry 1993 Dec

filter terms:

3-Cyano-2,6-dihydroxypyridine (CNDP) was identified as a potent inhibitor (IC50 value, 4.4 nM) of dihydrouracil dehydrogenase (DHUDase) [EC 1.3.1.2], a rate-limiting enzyme in 5-fluorouracil (5-FU) degradation. The inhibitory activity of CNDP was about 2,000 times that of uracil under our assay conditions. Kinetic analyses with partially purified enzyme from rat liver revealed that the mechanism of inhibition of DHUDase by CNDP was of mixed type with an inhibition constant (Ki) of 1.51 nM. CNDP had less effect on 5-FU phosphorylation than on 5-FU degradation. The inhibitory effect of CNDP on ribosylation of 5-FU was 600 to 1,000 times less than that on DHUDase. Moreover, CNDP did not inhibit uridine kinase, thymidine kinase, or pyrimidine phosphoribosyltransferase. Coadministration of CNDP with 1-ethoxymethyl-5-fluorouracil (EM-FU) to rats with Yoshida sarcoma elevated the level of 5-FU in both the blood and the tumor and enhanced the antitumor effect of EM-FU. These findings indicated that CNDP would be a useful chemical modulator in chemotherapy with 5-FU or its prodrugs.

Citation

K Tatsumi, T Yamauchi, K Kiyono, K Kishi, Y Yanagihara, T Imaoka, T Kawaguchi, M Kubo. 3-Cyano-2,6-dihydroxypyridine (CNDP), a new potent inhibitor of dihydrouracil dehydrogenase. Journal of biochemistry. 1993 Dec;114(6):912-8