- Last Update On : 2013-02-03
The troponin complex consists of three subunits: troponin T (tropomyosin binding), troponin I (inhibitory), and troponin C (calcium binding). This complex is located on the actin filament and regulates the calcium mediated interaction of actin and myosin filaments during muscular contraction. Most troponin T and I molecules are bound to the contractile proteins, but a small fraction (3 - 6%) remains free in the cytoplasm. Both troponin T and I have amino acid sequences that differ between adult skeletal and cardiac muscle. Immunoassays are now available that can specifically measure cardiac troponin T and I in plasma. Troponin C has no potential as a cardiac specific marker because its amino acid sequence is identical in skeletal and cardiac muscle.
Following cardiac injury, there is an early release of troponin from the cytoplasmic pool followed by a persistent release of the bound fraction from muscle fibers that are being degraded. Troponin levels become elevated within 2