Some kinetic singularities of Mg2+-dependent Mn-ATPase in rat brain synaptic membranes

Mn(2+) stimulated change of Mg-ATPase activity has been found in the synaptic fraction of rat brain that was named Mn-ATPase. Investigation of the molecular mechanism has shown that Mn-ATPase is a multi-sited enzyme system whose minimum functional unit is a dimer. Its substrate is the MgATP complex. The number of sites for Mn(2+) as for essential activators and that of full-effect inhibitors are equal, n = m = 1. Studying regulation of the Mn-ATPase system by Mg(2+) has shown that Mg(2+) represents a double-sided effect modifier, namely, it activates the enzyme system at low concentration but inhibits at high concentration. Supposedly, binding-release of MgATP and Mg(2+) from the enzyme would be performed by a randomized mechanism. When analyzing experiments by using the kinetic method of complex curves, a "minimal model" for Mn-ATPase has been created.