uridine catabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the breakdown of uridine, uracil riboside, a ribonucleoside very widely distributed but occurring almost entirely as phosphoric esters in ribonucleotides and ribonucleic acids. [GOC:go_curators]

Uridine catabolism is a crucial process for the breakdown of uridine, a pyrimidine nucleoside, into simpler compounds that can be reused or excreted. It plays a significant role in maintaining nucleotide homeostasis, regulating pyrimidine metabolism, and providing energy. Here's a detailed description of the biological process:

**1. Uridine Phosphorylation:**

* Uridine is first phosphorylated by uridine kinase to uridine monophosphate (UMP). This step requires ATP as a phosphate donor.

**2. UMP to UDP and UTP:**

* UMP is then converted to uridine diphosphate (UDP) by UDP-glucose pyrophosphorylase. This step requires the hydrolysis of ATP.
* UDP is further phosphorylated to uridine triphosphate (UTP) by nucleoside diphosphate kinase using ATP as a phosphate donor.

**3. Uridine Deamination:**

* UTP can undergo deamination to dihydrouracil by the enzyme cytidine deaminase.
* Dihydrouracil is then oxidized to uracil by dihydrouracil dehydrogenase.

**4. Uracil Catabolism:**

* Uracil is degraded through a two-step process:
* Uracil is first converted to dihydrouracil by dihydropyrimidine dehydrogenase.
* Dihydrouracil is then hydrolyzed to β-ureidopropionate by dihydrouracil hydrolase.

**5. β-ureidopropionate Breakdown:**

* β-ureidopropionate is further metabolized to β-alanine and carbon dioxide through the action of β-ureidopropionase.

**6. β-alanine Catabolism:**

* β-alanine can be either:
* Converted to acetyl-CoA, entering the citric acid cycle for energy production.
* Used as a building block for the biosynthesis of pantothenate, a precursor for coenzyme A.

**7. Regulation:**

* The uridine catabolic pathway is tightly regulated by various mechanisms, including:
* The availability of substrates, such as uridine and ATP.
* The activity of key enzymes, like uridine kinase, UDP-glucose pyrophosphorylase, and cytidine deaminase.
* The concentration of intracellular nucleotides, which can act as feedback regulators.

**Overall, the uridine catabolic process is a crucial pathway that ensures the proper turnover of uridine and other pyrimidines, maintaining cellular homeostasis and providing vital intermediates for energy production and other metabolic processes.**'
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Proteins (1)

Compounds (4)