The action of some orotic acid analogues on the in vitro incorporation of 14C-orotate into pyrimidine nucleotides

Abstract

The effect of some orotic acid analogues on the incorporation of 14C-orotate into uridine and cytidine nucleotides by a soluble rat liver enzyme system was investigated. The compounds studied were found to inhibit the labelling of uridine nucleotides in the following order: 5-azaorotic acid, orotic acid hydrazide, 2-thioorotic acid, uracil-6-aceticacid, orotaldehyde hydrazone, 4, 6-dihydroxypicolinicacid(“3-deazaoroticacid”). With the orotic acid hydrazide and the orotaldehyde hydrazone the labelling of cytidine nucleolides runs parallel to that of uridine nucleotides. With the four other compounds the inhibition of 14C-orotate incorporation into cytidine nucleotides is much stronger as compared to uridine nucleotides. This effect is more pronounced in the case of 2-thioorotic acid and uraeil-6-acetic acid.