[Calcium. Molecular mechanisms of cellular function].

Calcium plays a pivotal role in cellular signal transduction. Precise control and regulation of cytoplasmic free ionic calcium concentration is a prerequisite for intracellular calcium-mediated physiology. Calmodulin is the ubiquitous calcium receptor protein which conveys the information to the calcium-dependent enzymes. Protein kinase C and receptor-stimulated phosphatidylinositol metabolisms are components of another regulatory mechanism where calcium plays an important regulatory role, too. Oncogene products have been found to possess enzymatic activities involved in phosphatidylinositol metabolism.