orotate phosphoribosyltransferase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: orotidine 5'-phosphate + diphosphate = orotate + 5-phospho-alpha-D-ribose 1-diphosphate. [EC:2.4.2.10]

Orotate phosphoribosyltransferase (OPRT) activity catalyzes the transfer of a phosphoribosyl group from 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) to orotate, resulting in the formation of orotidine 5'-monophosphate (OMP). This reaction is a crucial step in de novo pyrimidine biosynthesis, a metabolic pathway responsible for the synthesis of the pyrimidine bases uracil and cytosine, essential components of DNA and RNA. OPRT activity is central to this pathway because it is the first committed step in the biosynthesis of pyrimidines.

The reaction proceeds in two steps:

1. **PRPP binding:** The enzyme binds both PRPP and orotate. PRPP is a highly reactive molecule, and its binding to OPRT likely induces conformational changes in the enzyme, facilitating the subsequent transfer reaction.
2. **Phosphoribosyl transfer:** The enzyme catalyzes the transfer of the phosphoribosyl group from PRPP to orotate, forming OMP. This reaction involves the cleavage of the pyrophosphate bond in PRPP, releasing inorganic pyrophosphate (PPi) as a byproduct.

The OPRT active site is characterized by a series of conserved amino acid residues that interact with the substrate molecules, PRPP and orotate. These interactions are crucial for substrate binding and catalysis.

OPRT activity is regulated by various factors, including the availability of substrates, the presence of inhibitors, and the cellular demand for pyrimidines. Dysregulation of OPRT activity can lead to various metabolic disorders, highlighting the importance of this enzyme in maintaining cellular homeostasis and normal physiological function.

This detailed description provides insights into the molecular function of OPRT activity, emphasizing its role in nucleotide biosynthesis and its significance in cell metabolism.'
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Proteins (1)

Compounds (4)