Coordinate behavior of orotate phosphoribosyltransferase and orotidylate decarboxylase in developing mouse liver and brain

A large body of data has accumulated in recent years supporting the view that orotate phosphoribosyltransferase and orotidylate decarboxylase exist as a bifunctional enzyme complex in adult mammalian tissues. This paper presents evidence that such a complex also occurs in mouse liver and brain, regardless of the developmental stage of the animal. Orotate phosphoribosyltransferase and orotidylate decarboxylase activities remained coordinate in fetal, neonatal, immature and adult liver and brain. In addition, these two enzymes routinely cosedimented during centrifugation of cell-free extracts in sucrose gradients. The sedimentation coefficient of the enzyme complex did not change significantly during mouse development. However, the liver complex exhibited a sedimentation coefficient (5.0 ± 0.2) that differed from that of the brain complex (4.3 ± 0.1)