purine nucleoside metabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways involving one of a family of organic molecules consisting of a purine base covalently bonded to a sugar ribose (a ribonucleoside) or deoxyribose (a deoxyribonucleoside). [GOC:jl, ISBN:0140512713]

Purine nucleoside metabolic process is a fundamental biological process that encompasses the synthesis, breakdown, and interconversion of purine nucleosides. Purine nucleosides are crucial building blocks of DNA and RNA, playing vital roles in genetic information storage, protein synthesis, and numerous other cellular functions.

**Purine Nucleoside Synthesis:**

1. **De novo synthesis:** This pathway begins with the formation of the purine ring from simple precursors, including amino acids, bicarbonate, and tetrahydrofolate. The key intermediates in this pathway are inosine monophosphate (IMP) and then guanosine monophosphate (GMP) and adenosine monophosphate (AMP).
2. **Salvage pathway:** This pathway utilizes preformed purine bases or nucleosides from the breakdown of nucleic acids or dietary sources. These salvage pathways are essential for maintaining adequate purine nucleotide pools, especially in tissues with high turnover, such as rapidly proliferating cells.

**Purine Nucleoside Breakdown:**

1. **Phosphorylation:** Purine nucleosides are first phosphorylated by kinases to generate their corresponding monophosphates (AMP, GMP).
2. **Degradation:** The purine monophosphates are then degraded through a series of enzymatic steps, ultimately generating uric acid, the primary end product of purine metabolism in humans.

**Regulation of Purine Nucleoside Metabolism:**

Purine nucleoside metabolism is tightly regulated to maintain appropriate nucleotide pools and prevent the accumulation of toxic intermediates. Key regulatory mechanisms include:

1. **Feedback inhibition:** The end products of purine synthesis (AMP and GMP) feedback inhibit the key enzymes in the de novo pathway.
2. **Allosteric regulation:** Various enzymes involved in purine metabolism are subject to allosteric regulation by metabolites and cofactors.
3. **Gene expression control:** The expression levels of genes encoding purine metabolic enzymes are regulated by a variety of factors, including cellular demands and nutrient availability.

**Clinical Relevance:**

Disruptions in purine nucleoside metabolism can lead to a variety of human diseases, including:

1. **Gout:** A painful inflammatory condition caused by the accumulation of uric acid crystals in the joints.
2. **Lesch-Nyhan syndrome:** A rare genetic disorder characterized by hyperuricemia, self-injurious behavior, and cognitive impairment.
3. **Immunodeficiency disorders:** Defects in purine metabolism can impair immune function due to disruptions in DNA and RNA synthesis.
4. **Cancer:** Aberrant purine metabolism is frequently observed in cancer cells, contributing to their uncontrolled growth and proliferation.'
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Proteins (1)

Compounds (1)