### PKM Gene Overview

**Gene Symbol:** PKM  
**Function:** The PKM gene encodes pyruvate kinase, which is a key regulatory enzyme in glycolysis. It catalyzes the conversion of phosphoenolpyruvate (PEP) to pyruvate, generating ATP in the process. The enzyme exists in two main forms: a highly active tetramer and a less active dimer, with the equilibrium between these forms playing a critical role in metabolic regulation, particularly in the context of cancer cell metabolism.

### Additional Information

1. **Associated Genes:**
   - **GLUT1 (SLC2A1):** Glucose transporter 1, as glucose metabolism is closely linked with glycolytic processes.
   - **HK (Hexokinase):** Involved in the initial step of glycolysis, influencing flux through the pathway along with PKM.
   - **PKM2 (an isoform):** While both PKM1 and PKM2 are splicing variants of the PKM gene, PKM2 is particularly discussed regarding its roles in cancer metabolism.
   - **Other glycolytic enzymes:** Such as Aldolase (ALDOA, ALDOB) and Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which may interact functionally with pyruvate kinase within the glycolytic pathway.

2. **Aging and Age-related Diseases:**
   - Research has indicated that alterations in glucose metabolism and glycolysis might affect aging and age-related diseases. Increased glycolytic activity has been associated with certain age-related pathologies, such as cancer and neurodegenerative diseases.
   - The balance between the PKM isoforms (PKM1 and PKM2) is often disrupted in cancer, and abnormal expression levels have been correlated with advanced aging and metabolic dysregulation.
   - There is potential for PKM to be involved in the aging-associated metabolic shift, although direct evidence linking PKM specifically to longevity or age-related diseases remains an emerging area of study.

3. **Drug and Drug Classes:**
   - **Chemotherapeutics:** Agents targeting tumor metabolism may affect PKM function and expression (e.g., dichloroacetate, which can alter pyruvate metabolism).
   - **Metformin:** Known to impact cellular metabolism and has been associated with changes in glycolysis which may involve PKM.
   - **Thyroid hormone modulators:** Given the interaction of PKM with thyroid hormone, certain drugs affecting thyroid function could have secondary effects on PKM activity.

4. **Pathways and Biological Processes:**
   - **Glycolysis:** PKM plays a central role in the glycolytic pathway, which is crucial for ATP production.
   - **Gluconeogenesis:** PKM is also involved, although primarily glycolytic functions are emphasized.
   - **Regulation of Metabolic Processes:** The tetrameric vs. dimeric forms of PKM influence the balance between biosynthetic pathways and ATP production, particularly in rapidly proliferating cells, like cancer cells.
   - **Effects of Thyroid Hormone:** Metabolic effects induced by thyroid hormones via interaction with PKM may influence energy homeostasis.
   - **Cellular respiration and energy production:** Via its role in glycolysis, influencing larger biological processes such as oxidative phosphorylation and respiratory metabolism.

### Summary
The PKM gene encodes an essential enzyme for energy metabolism and is intricately linked to various metabolic pathways and cellular processes. Its regulation has implications not just for basic metabolic needs but also for pathologies including cancer and potentially aging, marking it as a significant player in the metabolic landscape of health and disease. Current research continues to explore its broader implications in drug interactions and biological pathways.