Orotidine 5 -phosphate pyrophosphorylase and

P14 Pausch, J., Keppler, D. and Decker, K. Increased activities of hepatic orotidine 5 -phosphate pyrophosphorylase and orotidine 5 -phosphate decarboxylase induced by orotate. FEBS Lett. 20, 330-332 (1972)... 

The formation of the first nucleotide in the pyrimidine sequence, orotidylic acid (orotidine 5 -phosphate), was accomplished by the reaction of 5-phosphoribosyl-l-pyrophosphate (PRPP) with orotic acid 83) (Fig. 22). Other pyrimidines and carbamylaspartic acid did not react with PRPP in the presence of the enzyme, which has been named orotidine 5 -phosphate pyrophosphorylase. Several purine analogs, e.g., 6-uracilsulfonic acid, 6-uracil methyl sulfone, which inhibited the growth of several organisms (S78, 379), probably inhibited the formation of orotidylic acid. 

Orotidine S -monophosphate, OMPi a nucleotide of orotic acid. M, 368.2. OMP is an intermediate in Pyrimidine biosynthesis (see). Orotidine 5 -phos-phate pyrophosphorylase catalyses the synthesis of OMP from orotic add and S-phosphoribosyl 1-pyro-phosphate. 

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