Properties of pea seedling uracil phosphoribosyltransferase and its distribution in other plants |
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Authors: | Bressan R A Murray M G Gale J M Ross C W |
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Institution: | Department of Botany and Plant Pathology, Colorado State University, Fort Collins, Colorado 80523. |
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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 MgCl2 for maximum activity but was inhibited by MnCl2; its molecular weight determined by chromatography on Sephadex G-150 columns was approximately 100,000; its Km values for uracil and 5-phosphorylribose 1-pyrophosphate were 0.7 μm and 11 μm; 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. |
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