Interaction of NAD-dependent dehydrogenases with human erythrocyte membranes

Interaction of D-glyceraldehyde-3-phosphate dehydrogenase (GPDH) and ladate dehydrogenase with human erythrocyte membranes was studied. Under the conditions of low ionic strength, both enzymes bound to the membranes with similar affinities (Kd ≈ 1 μM). The binding was accompanied by complete inhibition of GPDH and by a 65–75% inhibition of ladate dehydrogenase (LDH). Increasing the ionic strength to physiologically meaningful values (0.15M) completely abolished the inactivation of both dehydrogenases in the presence of erythrocyte membranes, but did not preclude their binding. These results suggest that different modes of enzyme-membrane interaction can be realized under the conditions of low and high ionic strength. They also indicate that GPDH and LDH are capable of functioning in a membrane-bound state.