### PEPD Gene Overview

**Gene Symbol:** PEPD  
**Gene Location:** Chromosome 19 (19p13.2)  
**Protein:** Prolidase (also known as dipeptidase I)  
**Function:** The PEPD gene encodes an enzyme that is crucial for the hydrolysis of dipeptides and tripeptides containing proline or hydroxyproline residues at the C-terminus. It plays a pivotal role in proline recycling and collagen metabolism, which is essential for connective tissue integrity.

### Additional Associated Genes
While the NCBI and UniProt summaries do not specify additional genes, the following are known to be related to the PEPD gene:
- **COL1A1 and COL1A2**: Genes encoding the collagen type I alpha 1 and alpha 2 chains, respectively. These are directly associated with proline metabolism and collagen synthesis, where prolidase activity may influence collagen formation.
- **PYCR1, PYCR2, and PYCRL**: Genes that encode pyrroline-5-carboxylate reductases involved in proline metabolism.

### Aging and Age-Related Diseases
1. **Collagen Metabolism**: Given PEPD's role in collagen metabolism, it can be linked to aging; degradation of collagen is associated with wrinkles and loss of skin elasticity.
2. **Fibrosis**: Impaired prolidase activity could potentially contribute to fibrotic diseases which are more common as individuals age. Prolidase deficiency has been observed in conditions leading to excessive collagen deposition.
3. **Prolidase Deficiency**: This genetic disorder may present in childhood, but late-onset cases could be relevant in older adults leading to complications such as chronic renal failure or other age-related health issues.

### Drug Interactions
Currently, there is no definitive list of specific drugs targeting PEPD. However, drugs that may indirectly influence collagen metabolism or matrix metalloproteinases (MMPs) might modulate the consequences of altered prolidase activity. Research into therapeutic agents for prolidase deficiency is ongoing, though specifics are limited.

### Pathways and Biological Processes
1. **Collagen Biosynthesis**: PEPD is integral in the synthesis and remodeling of collagen, helping to maintain connective tissue integrity.
2. **Amino Acid Metabolism**: It is involved in the catabolism of dipeptides, particularly those containing proline residues.
3. **Proline Metabolism Pathway**: Prolidase plays a crucial part in recycling proline, ensuring availability for various cellular functions.
4. **Metabolism of Amino Acids and Derivatives**: It participates in larger metabolic pathways related to amino acids, contributing to nitrogen metabolism.

### Summary
The PEPD gene is essential for collagen metabolism and proline recycling. Mutations can lead to prolidase deficiency, affecting overall health. Its association with collagen disorders highlights its potential role in aging and related diseases. While specific drug interactions remain unclear, ongoing research may reveal more about its therapeutic targeting.