### PGK2 Gene Summary

**Gene Symbol:** PGK2  
**Location:** Human chromosome 14

The PGK2 gene encodes a protein that is a member of the phosphoglycerate kinase family. Unlike its paralog PGK1, PGK2 is specifically expressed in the testis and is crucial during the later stages of spermatogenesis. The retrotransposition event that gave rise to PGK2 led to its intronless structure, and it is a functional gene involved in the glycolytic pathway, specifically catalyzing the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate.

### Additional Information:

#### 1. Associated Genes
While PGK2 itself does not have an extensive list of directly associated genes, it is related to the following genes:
   - **PGK1:** The non-testis specific paralog, which also encodes a phosphoglycerate kinase and is involved in glycolysis and energy metabolism.
   - **AKAP4:** A gene involved in the anchoring of protein kinase A and implicated in sperm motility and function, which may be functionally linked to pathways involving PGK2.

#### 2. Aging and Age-Related Diseases
As of October 2023, there is limited specific research directly linking PGK2 to aging or age-related diseases. However, general principles of energy metabolism and fertility suggest implications; for example, declines in testicular function or sperm quality are linked to aging and may indirectly relate to PGK2 function. Further research could elucidate connections between PGK2 function, age-related declines in fertility, and metabolic stress on spermatogenesis.

#### 3. Drugs and Drug Classes
Currently, there are no specific drugs or drug classes directly associated with PGK2 known to interact. However, since phosphoglycerate kinases are implicated in various metabolic disorders, it could be relevant in the context of pharmacological interventions targeting glycolysis, though detailed relationships have yet to be established.

#### 4. Pathways and Biological Processes
PGK2 is primarily involved in:
- **Glycolysis:** The Embden-Meyerhof-Parnas pathway where it catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, a key step in energy production during sperm maturation.
- **Spermatogenesis:** Although not required for the completion of spermatogenesis, the enzyme’s activity is crucial for sperm motility, highlighting its role in male fertility.

### Conclusion
The PGK2 gene plays a specialized role in male reproductive biology, specifically in the energy metabolism required for sperm function. Its unique expression and functional characteristics differentiate it from PGK1, emphasizing its importance in testicular biology. Further studies may help strengthen understanding of its impact on male fertility and possibly its connections to age-related parameters of reproductive health.