Evidence for the localization of the mitochondrial glycerol-phosphate dehydrogenase in the outer phase of the inner membrane is presented.
- 1Glycerol-phosphate does not permeate through the inner membrane to the matrix space in a number of mitochondria which actively oxidize glycerol-phosphate.
- 2The impermeability of the inner membrane to ferricyanide is demonstrated and this forms a basis for elucidating membrane localization of carriers.
- 3In mitochondria from various tissues ferricyanide can interact directly with glycerolphosphate dehydrogenase but not with succinate dehydrogenase.
- 4The oxidation of glycerol-phosphate, in contrast to that of succinate, is insensitive to substrate depletion brought about by uncouplers.
- 5The results are interpreted to show that both the substrate and the acceptor-site of glycerol-phosphate dehydrogenase are exposed to the outer side of the inner membrane. Thus, for the operation of the glycerol-phosphate dehydrogenase, mitochondria do not require translocases for glycerol-phosphate and dihydroxyacetone-phosphate.