orotidine-5'-phosphate decarboxylase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: H+ + orotidine 5'-phosphate = CO2 + UMP. [EC:4.1.1.23, RHEA:11596]

Orotidine-5'-phosphate decarboxylase (ODCase) is an enzyme that catalyzes the decarboxylation of orotidine-5'-phosphate (OMP) to uridine-5'-monophosphate (UMP), a crucial step in the de novo biosynthesis of pyrimidine nucleotides. The reaction involves the removal of a carboxyl group from the C6 position of OMP, resulting in the formation of the double bond between C5 and C6, thereby generating UMP.

This enzymatic activity is essential for the synthesis of UMP, which serves as a precursor for the formation of other pyrimidine nucleotides, including cytidine triphosphate (CTP), thymidine triphosphate (TTP), and uridine diphosphate (UDP). These nucleotides are fundamental building blocks of DNA and RNA, playing vital roles in various cellular processes, including replication, transcription, translation, and energy metabolism.

The mechanism of action of ODCase involves a two-step process:

1. **Protonation of the carboxyl group:** The enzyme first protonates the carboxyl group of OMP, facilitating its removal. This step is typically mediated by a conserved histidine residue within the active site of the enzyme.
2. **Decarboxylation and elimination:** The protonated carboxyl group undergoes decarboxylation, releasing carbon dioxide. The resulting carbanion intermediate is then stabilized by a nearby positively charged residue, usually an arginine or lysine. This stabilization allows for the elimination of the carbanion, resulting in the formation of the double bond between C5 and C6 of UMP.

The precise mechanism and catalytic residues involved can vary slightly depending on the specific ODCase enzyme. However, the overall principle of protonation, decarboxylation, and elimination remains consistent across different species.

In summary, the molecular function of orotidine-5'-phosphate decarboxylase activity is essential for the biosynthesis of pyrimidine nucleotides, which are vital for DNA and RNA synthesis and various cellular processes. The enzyme catalyzes the decarboxylation of OMP to UMP through a two-step mechanism involving protonation, decarboxylation, and elimination, ultimately contributing to the maintenance of cellular function and genetic integrity.'
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Proteins (1)

Compounds (4)