An approach to the elucidation of the quaternary structure role in the activity of pyruvate kinase studies on the immobilized enzyme.

1. Studies on pyruvate kinase immobilized via -S-S- linkages showed that single subunits of this tetrameric enzyme are inactive. 2. Pyruvate kinase was coupled with different preparations of CNBr-activated Sepharose via one and more than one bond, and after removal of non-covalently bound subunits by denaturant treatment the subunit derivatives were obtained composed of different pyruvate kinase species. 3. Heat inactivation studies of immobilized enzyme derivatives suggested that not only tetramers of pyruvate kinase are active. 4. This idea is further supported by experiments with 2 M urea dissociation of immobilized tetrameric enzyme carried out in the presence of Mg2+ ions.