Calcium messenger system


Rasmussen in 1970 suggested that calcium should be regarded as a secondary messenger in the same way that cAMP is regarded. Since his observation, a lot of information confirming is hypothesis has been found). It has originally been noted that Ca2+ regulated the activity of the enzyme phosphodiesterase (PE) which hydrolyses cAMP to inactive AMP. Later on a specific protein which helps to confer regulative ability on PDE was discovered and called calmodulin. Other calcium receptor proteins has been discovered e.g. troponine. However, calmodulin is universally distributed in plant and animal cells and hence its universal nature as a calcium receptor has been widely acknowledged.

            Two methods of Ca2+ modulation are generally recognized.

  • a.         amplitude modulation

b.                   sensitivity modulation

Amplitude modulation occurs where hormone binds to the calcium receptor which then triggers off a mechanism for concentration of Ca2+ in the cytosol with the binding of calcium to receptors.











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