Catalyzes the conversion of dihydroorotate to orotate with quinone as electron acceptor. Required for UMP biosynthesis via de novo pathway. (S)-dihydroorotate + a quinone = a quinol + orotate Binds 1 FMN per subunit. Pyrimidine metabolism; UMP biosynthesis via de novo pathway; orotate from (S)-dihydroorotate (quinone route): step 1/1. Monomer. The uncleaved transit peptide is required for mitochondrial targeting and proper membrane integration. Belongs to the dihydroorotate dehydrogenase family. Type 2 subfamily.