PREFERENTIAL HYDRATION OF LACTATE DEHYDROGENASE IN CONCENTRATED SALT SOLUTIONS

1. 1. Beef heart lactate dehydrogenase (l-lactate:NAD oxidoreductase, EC 1.1.1.27) isoenzyme H4 does not dissociate at low enzyme concentrations. This result differs from some previously published data but is in agreement with the work of Wieland et al.3 and of Pesce et al.4. 2. 2. The enzymatically active unit is the tetramer; inhibition by excess of pyruvate occurs without enzyme dissociation. 3. 3. As shown by Millar2 the apparent sedimentation coefficient of the enzyme decreases when the NaCl concentration increases, but this effect does not arise from the dissociation of the tetrameric form. The present work demonstrates that preferential hydration is responsible for this variation. © 1969.