[Quaternary structure of NAD-kinase from rabbit skeletal muscles]

The quaternary structure and some kinetic properties were studied for NAD-kinase from the rabbit skeletal muscles. The molecular weight of the 150-300-fold purified enzymic preparation was determined by separation in the Sephadex G-200 thin layer, by means of Sephadex G-200 column gel-filtration and by the method of electrophoresis in the gradient of polyacrylamide gel concentration. Some molecular forms of NAD-kinase with a molecular weight of 31000-305000 are found in the enzymic preparation and possibility to change from one form to another is shown. On the basis of the established quaternary structure and complex kinetic characteristics of the enzyme a conclusion is drawn on the existence of the rabbit skeletal muscle NAD-kinase as an equilibrium system of the oligomeric forms possessing different catalytic activity and consisting of different combinations of subunits with a molecular weight of 31000.