title: Properties of pea seedling uracil phosphoribosyltransferase and its distribution in other plants.
abstract: A uracil phosphoribosyltransferase (UMP-pyrophosphorylase) was found in several angiosperms and was partially purified from epicotyls of pea (Pisum sativum L. cv. Alaska) seedlings. Its pH optimum was about 8.5; its required approximately 0.3 mm MgCl(2) for maximum activity but was inhibited by MnCl(2); its molecular weight determined by chromatography on Sephadex G-150 columns was approximately 100,000; its K(m) values for uracil and 5-phosphorylribose 1-pyrophosphate were 0.7 mum and 11 mum; and it was partially resolved from a similar phosphoribosyltransferase converting orotic acid to orotodine 5'-phosphate. Enzyme fractions containing both uracil phosphoribosyl transferase and orotate phosphoribosyltransferase converted 6-azauracil and 5-fluorouracil to products with chromatographic properties of 6-azauradine 5'-phosphate and 5-fluorouridine 5'-phosphate. Uracil phosphoribosyltransferase probably functions in salvage of uracil for synthesis of pyrimidine nucleotides.
authors: Department of Botany and Plant Pathology, Colorado State University, Fort Collins, Colorado 80523.
authors: R A
authors: RA
authors: Bressan
authors: M G
authors: MG
authors: Murray
authors: J M
authors: JM
authors: Gale
authors: C W
authors: CW
authors: Ross