<prompt> The enzyme catalyzing the production of orotidylic acid is?Aspayl transcarbamoylaseDihydro orotaseDihydro orotate dehydrogenaseOrotate phosphoribosyl transferase  <response>: In the de novo synthesis of pyrimidines, the enzyme aspayl transcarbamoylase catalyses the combination of carbamoyl phosphate and aspaate to form carbamoyl aspaate. Dihydro orotase catalyses the production of dihydro orotic acid. Dihydro orotate dehydrogenase catalyses the production of orotic acid from dihydro orotic acid. Orotate phosphoribosyl transferase is the enzyme catalyzing the synthesis of orotidylic acid Orotidine 5-monophosphate. Ref: Textbook of Biochemistry, D. M. Vasudevan Sreekumari S, 4th edition, page 394. 