title: [The nature of the pyrimidine substrate of 6,7-dimethyl-8-ribityllumazine synthase participating in riboflavin biosynthesis in yeasts].
abstract: 2,4-dihydroxy-5-amino-6-ribitylaminopyrimidine and 2,4-dihydroxy-5-amino-6-ribitylaminopyrimidine-5'-phosphate are studied for their effect on the activity of 6,7-dimethyl-8-ribityllumazine synthase of Pichia guilliermondii yeasts. It is shown that when nonphosphorylated form of pyrimidine and ribose-5-phosphate (donor C-4--a fragment) is used as a substrate, the specific activity of 6,7-dimethyl-8-ribityllumazine synthase is high and Be2+ and F- ions, inhibitors of alkaline phosphatases, do not inhibit it. The value of Km for this pyrimidine is 1.1 X 10(-5) M. Phosphorylated pyrimidine being used as a substrate in the presence of Be2+ and F-, the reaction practically does not proceed. Therefore, only 2,4-dihydroxy-5-amino-6-ribitylaminopyrimidine is a pyrimidine substrate of 6,7-dimethyl-8-ribityllumazine synthase of yeast.
mesh_terms: D009097:Multienzyme Complexes / Q000378:metabolism*; D010766:Phosphorylation; D010843:Pichia / Q000201:enzymology* / Q000378:metabolism; D011743:Pyrimidines / Q000378:metabolism*; D012256:Riboflavin / Q000096:biosynthesis*; D004718:Saccharomycetales / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D009097:Multienzyme Complexes; D011743:Pyrimidines; C044822:6,7-dimethyl-8-ribityllumazine synthase; D012256:Riboflavin
vernacular_title: O prirode pirimidinovogo substrata 6,7-dimetil-8-ribitilliumazinsintazy, uchastvuiushcheĭ v biosinteze riboflavina u drozhzheĭ.