Lactate Dehydrogenase (LDH)

Lactate Dehydrogenase (LDH)

Definition: Lactate dehydrogenase (LDH) is an enzyme involved in the conversion of lactate to pyruvate and vice versa, playing a crucial role in anaerobic metabolism. It is found in nearly all tissues of the body, with particularly high concentrations in the heart, liver, kidneys, bone and skeletal muscles.

Functions of Lactate Dehydrogenase

• Energy Production:

• LDH catalyzes the conversion of pyruvate to lactate during anaerobic respiration, allowing for ATP production when oxygen levels are low.

• Metabolic Regulation:

• It helps regulate the balance between aerobic and anaerobic metabolism, influencing energy production based on oxygen availability.

• Lactate Clearance:

• LDH facilitates the conversion of lactate back to pyruvate, which can then enter the Krebs cycle for further energy production when oxygen becomes available.

Isoenzymes of Lactate Dehydrogenase

LDH exists as five different isoenzymes (LDH-1 to LDH-5), each with varying distributions in tissues:

• LDH-1: Predominantly found in the heart.
• LDH-2: Found in reticuloendothelial tissues.
• LDH-3: Present in lungs and other tissues.
• LDH-4: Found in kidneys and placenta.
• LDH-5: Primarily located in skeletal muscle and liver.

Regulation of LDH Levels

• Physiological Factors: LDH levels can vary based on age, sex, and physical activity.
• Pathological Conditions: Elevated LDH levels can indicate tissue damage or disease states such as myocardial infarction, liver disease, hemolysis, and certain blood cancer and solid organ tumor.

Clinical Relevance

• Diagnosis of Myocardial Infarction:

• LDH levels are measured alongside other cardiac markers to assess heart damage following a heart attack.

• Assessment of Tissue Damage:

• Elevated LDH levels can indicate damage to various tissues, including liver and skeletal muscle injuries.

• Monitoring Cancer Progression:

• Increased LDH levels may be associated with solid organ tumor burden and can be used to monitor certain malignancies.

Conclusion

Lactate dehydrogenase is a vital enzyme involved in energy metabolism and is clinically significant for diagnosing and monitoring various health conditions related to tissue damage and metabolic disorders.

References

1. Lentz SR. “Lactate Dehydrogenase.” Clinical Chemistry. 1996; 42(8): 1284-1289.
2. Thygesen K, et al. “Fourth Universal Definition of Myocardial Infarction (2018).” Journal of the American College of Cardiology. 2018; 72(18): 2231-2264. DOI: 10.1016/j.jacc.2018.08.1038
3. Karpati G, et al. “Creatine Kinase Deficiency.” The New England Journal of Medicine. 1980; 303(23): 1361-1367. DOI: 10.1056/NEJM198012043032301