The effects of some mitochondrial translocase inhibitors on the activity of rat liver transhydrogenase.

Non-energy dependent transhydrogenase activity in submitochondrial particles is stimulated at pH 8 by some inhibitors of mitochondrial carboxylate translocases. On solubilising the enzyme or assaying it at pH 6 these inhibitors have little effect. Km values remain unchanged under all these conditions. Conversely, energy-dependent transhydrogenase activity is inhibited by these substances possibly due to their direct action on proton transport. It is suggested that the observed effects may all be due to changes in membrane conformation induced by the inhibitors.