Orotidylate decarboxylase of yeast and man.

摘要: Publisher Summary This chapter discusses orotidylate decarboxylase of yeast and man. Uridylic acid (UMP) biosynthesis is essential for most living organisms, providing the precursor three pyrimidine trinucleotides as well synthesis di- polysaccharides that utilize UTP lipids which require CTP. The amounts UDP sugars in mammalian liver can equal amount UTP. In man other animals, last two enzyme reactions de novo pathway are catalyzed by a single protein, UMP synthase. bifunctional protein has both orotate phosphoribosyltransferase activities. bacteria, six genes code monofunctional proteins catalyze required reactions. fungi, such yeast, there only five first enzymes packaged into large polypeptide, whereas remaining four monofunctional. mechanism ODCase appears to involve formation zwitterion OMP ylid on decarboxylation. Thiamin pyrophosphate catalyzes various decarboxylation transfer involving ketone groups because thiazolium ring with its positively charged N atom can, loss proton from adjacent C-2, generate adds carbonyl produce substrate ylid.