- A small, ubiquitous eukaryotic protein that binds calcium ions, thereby becoming the agent for many of the cellular effects long ascribed to calcium ions. This calcium-protein complex binds to the apoenzyme, to form the holoenzyme, of certain phosphodiesterases; through these, or other as yet unknown mechanisms, the complex regulates adenylate and guanylate cyclase s, many kinases, phospholipase A2 activity, and other basic cellular functions. [calcium + modulate]
* * *cal·mod·u·lin .kal-'mäj-ə-lən n a calcium-binding protein that mediates cellular metabolic processes (as muscle-fiber contraction) by regulating the activity of specific calcium-dependent enzymes
* * *cal·mod·u·lin (kal-modґu-lin) a ubiquitous calcium-binding protein of eukaryotic cells that mediates a variety of cellular responses to calcium. The calcium-calmodulin complex acts as a messenger, affecting the activity of many enzymes and nonenzyme proteins, including the calcium pump, numerous specific protein kinases and cyclic nucleotide phosphodiesterases, spectrin, histones, and tubulin.
Medical dictionary. 2011.