Jane-Jane Chen, Mary-Ellen Jones
Sep 1, 1976
Citations
2
Influential Citations
126
Citations
Quality indicators
Journal
Archives of biochemistry and biophysics
Abstract
Abstract Dihydroorotate dehydrogenase from rat liver is found to be located on the outer surface of the inner membrane of mitochondria. Dihydroorotate can diffuse freely from the cytosol into the mitochondria. Orotate can also diffuse freely from the mitochondria into the cytosol for futher conversion to UMP. Therefore, no active transport of either dihydroorotate or orotate is required in pyrimidine biosynthesis. The K m for l -dihydroorotate is 5.2 ± 0.6 μ m . pd -Dihydroorotate is not a substrate for the enzyme but is a competitive inhibitor with a K i of 1.4 m m . Of the compounds tested as analogs for dihydroorotate or metabolites related to pyrimidine biosynthesis, orotate is the strongest inhibitor, with a K i of 8.4 μ m . The K i values for 2,4-dinitrophenol and barbiturate are 180 and 56 μ m , respectively.