Magnesium and regulation of carbohydrate metabolism at the molecular level

Enzymatic reactions involving the transfer of high-energy phosphate require a divalent metal ion as a participant. This is normally Mg2+ in biological situations, as its level within the cell is greater than other divalent metal ions. Although available methods for determining free cellular Mg2+ have thus far given divergent results, there is a growing body of evidence that its concentration is relatively low, approximately 0.5 mM. This low level permits control of important parts of carbohydrate metabolism, especially glycolysis, by Mg2+. The role of Mg2+ in regulating the phosphoryl-transfer enzymes of this pathway is described. Also described briefly is a series of computer models of this metabolism in heart and pancreatic islets. These models indicate considerable changes in Mg2+ level, and consequent control, especially when there are sharp changes in the glycolytic rate.