Figure 1.

The de novo pyrimidine biosynthesis pathway, which leads to the formation of UMP. In subsequent steps, UMP is further converted into UDP and UTP (red words). DHODH catalyzes a redox reaction in which dihydroorotate is oxidized to orotate, while FMN is reduced to FMNH2, which is then re-oxidized by CoQ (ubiquinone). DHODH = dihydroorotate dehydrogenase.