nucleoside salvage

Definition

Target type: biologicalprocess

Any process which produces a nucleotide, a nucleobase linked to either beta-D-ribofuranose (ribonucleoside) or 2-deoxy-beta-D-ribofuranose (a deoxyribonucleotide), from derivatives of it without de novo synthesis. [GOC:jl]

Nucleoside salvage is a crucial metabolic pathway that allows cells to recover and reuse pre-existing purine and pyrimidine nucleosides and bases, rather than synthesizing them de novo. This process conserves energy and resources, particularly when de novo synthesis is limited.

The process involves several key steps:

1. **Uptake:** Cells actively transport nucleosides and bases from the extracellular environment into the cytoplasm via specific membrane transporters.

2. **Phosphorylation:** Once inside the cell, nucleosides are phosphorylated to their corresponding nucleoside monophosphates (NMPs) by specific kinases. For example, adenosine kinase phosphorylates adenosine to AMP.

3. **Conversion to Nucleotides:** NMPs are then further phosphorylated to nucleoside diphosphates (NDPs) and finally to nucleoside triphosphates (NTPs) by specific kinases. This step requires energy, often provided by ATP.

4. **Base Salvage:** Free purine bases, like guanine and hypoxanthine, can also be salvaged. They are first converted to their respective monophosphate forms by specific enzymes: hypoxanthine-guanine phosphoribosyltransferase (HGPRT) for guanine and hypoxanthine, and adenine phosphoribosyltransferase (APRT) for adenine.

**Key Enzymes:**

* **Adenosine Kinase:** Phosphorylates adenosine to AMP.
* **Guanosine Kinase:** Phosphorylates guanosine to GMP.
* **Hypoxanthine-guanine phosphoribosyltransferase (HGPRT):** Converts hypoxanthine and guanine to IMP and GMP, respectively.
* **Adenine phosphoribosyltransferase (APRT):** Converts adenine to AMP.

**Significance:**

* **Efficient Resource Utilization:** Nucleoside salvage conserves cellular resources by recycling pre-existing nucleosides and bases.
* **Metabolic Flexibility:** It allows cells to adapt to fluctuating levels of nucleotides and maintain a balanced pool for DNA and RNA synthesis.
* **Genetic Disorders:** Deficiencies in key salvage enzymes, like HGPRT, can lead to genetic disorders like Lesch-Nyhan syndrome.

Overall, nucleoside salvage is an essential pathway for maintaining nucleotide homeostasis and supporting cellular growth and function.'
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Proteins (2)

Compounds (2)