[Metabolism and action of intracellular magnesium (author's transl)]

The activity of Mg2+-activated enzymes shows a bell shaped pMg dependency, with a pMg optimum at 3. Intracellular Mg2+ concentrations, determined by different methods, are about 10(-3) mol/1. Thus Mg2+-dependent enzymes are optimally activated, or nearly so, with Mg2+. If the substrates of an enzyme form complexes with Mg2+ of different stabilities, and if free substrate and the substrate-Mg2+ complex react differently with the enzyme, the equilibrium will change with the concentration of Mg2+. When the extracellular concentration of Mg2+ is increased, Mg2+ becomes bound practically exclusively to the cell membrane. In Mg2+ deficiency, the intracellular concentrations of Na+, K+, Ca2+ and cycl. AMP are changed, and the rates of synthesis of DNA, RNA and protein are decreased.