MgATP

MgATP is the magnesium salt form of adenosine triphosphate (ATP). In living cells, ATP binds magnesium to form MgATP2−, the predominant form of the nucleotide under physiological conditions.

Chemistry: ATP is a triphosphorylated nucleoside; the triphosphate chain carries multiple negative charges. Mg2+ coordinates with oxygens on the phosphate groups, usually binding to the beta- and gamma-phosphates and to several nonbridging oxygens. This coordination reduces electrostatic repulsion, stabilizes the molecule, and orients it for hydrolysis and phosphate-transfer reactions that underlie energy transduction.

Formation and concentration: In cells, free Mg2+ is typically around 0.5–1 mM, and most ATP exists as MgATP. The MgATP population supports enzyme catalysis, and the balance between MgATP and MgADP shifts with metabolic state, pH, and overall Mg2+ availability. The Mg2+ complex is generally the form recognized by enzymes that use ATP.

Biological role: MgATP serves as a substrate for a wide range of enzymes, including kinases, ATPases, polymerases, and motor proteins. Its hydrolysis to MgADP and inorganic phosphate provides the energy required for phosphorylation events, muscle contraction, transport processes, and macromolecular synthesis. Magnesium binding also helps stabilize the negative charges on the triphosphate chain and can participate directly in catalytic mechanisms.

In research and medicine: MgATP is commonly supplied in biochemical assays as the active substrate. Understanding MgATP formation and Mg2+ homeostasis is important for interpreting ATP-dependent processes in cells and for studying enzymatic mechanisms that rely on MgATP.