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)
| Protein | Definition | Taxonomy |
|---|---|---|
| Uridine phosphorylase 1 | A uridine phosphorylase 1 that is encoded in the genome of human. [PRO:DNx, UniProtKB:Q16831] | Homo sapiens (human) |
Compounds (4)
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| doxifluridine | doxifluridine : A pyrimidine 5'-deoxyribonucleoside that is 5-fluorouridine in which the hydroxy group at the 5' position is replaced by a hydrogen. It is an oral prodrug of the antineoplastic agent 5-fluorouracil. Designed to circumvent the rapid degradation of 5-fluorouracil by dihydropyrimidine dehydrogenase in the gut wall, it is converted into 5-fluorouracil in the presence of pyrimidine nucleoside phosphorylase. | organofluorine compound; pyrimidine 5'-deoxyribonucleoside | antimetabolite; antineoplastic agent; prodrug |
| 5-benzylacyclouridine | 5-benzyl-1-(2-hydroxyethoxymethyl)uracil : A pyrimidone that is uracil which is substituted by a 2-hydroxyethoxymethyl group at position 1 and a benzyl group at position 5. 5-benzylacyclouridine: structure given in first source | hydroxyether; primary alcohol; pyrimidone | |
| 3-cyano-6-hydroxy-4-methyl-2-pyridone | 3-cyano-6-hydroxy-4-methyl-2-pyridone: structure in first source | ||
| 2,6-dihydroxy-3-cyanopyridine | 2,6-dihydroxy-3-cyanopyridine: inhibitor of 5-fluorouracil degradation |