Calcium and its Protein Binding in Lactation in Mammary Gland and Blood Clotting

Ca2+ ions are central to a complex intracellular messenger system that is mediating a wide range of biological processes: muscle contraction, secretion, glycolysis and gluconeogenesis, ion transport, cell division and growth. Ca2+ ions are also known to play various roles outside cells .Ca2+ ions are instrumental in joining certain proteins in the blood-clotting system with membrane surfaces of circulating cells. An important class of transport proteins is the Ca2+-ATPases, which are particularly abundant in muscle cells. In higher organisms, the Ca2+ concentration in extracellular fluids generally is considerably higher than the intracellular concentrations. The mammary glands produce, among other substances, a Ca2+-binding enzyme activator, α-lactalbumin, that has about 40 percent sequence identity with lysozyme. This protein, which is involved in the conversion of glucose into lactose, is secreted in large quantities, and in human milk constitutes some 15 percent of total protein. Ca2+ ions are involved in the cascade of enzymatic events that results in blood clotting in mammals.