REGIONAL MAPPING OF THE GENE ENCODING DIHYDROOROTATE DEHYDROGENASE, AN ENZYME INVOLVED IN UMP SYNTHESIS, ELECTRON-TRANSPORT, AND SUPEROXIDEGENERATION, TO HUMAN-CHROMOSOME REGION-16Q22

De novo UMP synthesis is a critical metabolic pathway for nucleic acid synthesis and for a variety of metabolic pathways. The pathway is a t arget for many widely used cancer chemotherapy agents, several of whic h are pyrimidine analogs. Humans and cattle have been described with m utations in UMP synthesis that lead to serious inborn errors of metabo lism. Dihydroorotate dehydrogenase (EC 1.3.3.1) (DHODH) carries out th e fourth committed step in the pathway and may also be important for m itochondrial electron transport and oxygen radical metabolism. We repo rt here that the gene encoding this enzyme in humans is located in the chromosomal region 16q22. With the mapping of DHODH, the mapping of a ll the steps of UMP synthesis is complete. All three genes involved ma p to different human chromosomes. This information is important in con sideration of regulation of UMP synthesis in mammals, including humans .