Isoenzymes and their therapeutic and diagnostic applications
Isoenzymes, also known as isozymes, are different forms of an enzyme that catalyze the same chemical reaction but have slightly different physical and/or chemical properties. Isoenzymes are produced by the same organism, but they may have different amino acid sequences or be encoded by different genes.
Isoenzymes can arise from several mechanisms, such as alternative splicing of mRNA, post-translational modifications, or gene duplication events followed by divergent evolution. These processes can lead to enzymes that have similar catalytic activity but differ in their substrate specificity, pH optimum, thermal stability, or regulation.
Isoenzymes can be detected and separated based on their unique physical or biochemical properties. Electrophoresis is a common technique used to separate and identify isoenzymes based on their differences in charge, size, or isoelectric point. Other methods include chromatography, immunoassays, and mass spectrometry.
Therapeutic and diagnostic applications
Isoenzymes have important diagnostic and therapeutic applications in medicine. Here are a few examples:
- Diagnosis of diseases: Isoenzymes are often used as diagnostic markers for diseases because different tissues or organs express specific sets of isoenzymes. For example, the measurement of serum levels of cardiac troponin I and creatine kinase MB isoenzyme (CK-MB) is used to diagnose myocardial infarction (heart attack). Similarly, the measurement of serum alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) levels can help diagnose liver and bone diseases.
- Prognosis of diseases: Isoenzymes can also be used to predict the outcome of a disease or the response to therapy. For example, the ratio of two isoenzymes of lactate dehydrogenase (LDH) can help predict the outcome of testicular cancer. Similarly, the ratio of alpha-fetoprotein (AFP) to des-gamma-carboxy prothrombin (DCP) isoenzyme is used to predict the recurrence of hepatocellular carcinoma.
- Monitoring of therapy: Isoenzymes can be used to monitor the response to therapy or the recurrence of a disease. For example, the measurement of serum prostate-specific antigen (PSA) levels can help monitor the response to therapy in prostate cancer patients. Similarly, the measurement of serum thyroglobulin (Tg) levels can help monitor the recurrence of thyroid cancer.
- Targeted therapy: Isoenzymes can be targeted by drugs to achieve selective effects on specific tissues or organs. For example, selective inhibitors of cyclooxygenase-2 (COX-2) isoenzyme are used to treat inflammation and pain while minimizing the side effects of non-specific COX inhibitors.
Overall, isoenzymes play a crucial role in the diagnosis, prognosis, monitoring, and treatment of various diseases. The development of more selective and specific methods to detect and target isoenzymes is likely to lead to further advances in personalized medicine.
First Year Pharm D Subjects Syllabus, Notes, PDF Books, MCQ
|Human Anatomy and Physiology
|Pharmaceutical Organic Chemistry
|Pharmaceutical Inorganic Chemistry
|Remedial Mathematics/ Biology