Intramitochondrial Localization of the Nicotinamide Adenine Dinucleotide- and Nicotinamide Adenine Dinucleotide Phosphate-dependent Xylitol Dehydrogenases

The two mitochondrial xyhtol dehydrogenases of guinea pig liver have been studied with a view to determining their intramitochondrial locations.By procedures involving swelling, shrinking, and sonic oscillation of the particles, followed by centrifugation in a discontinuous sucrose gradient, preparations representing solubilized enzymes, outer membranes, and inner fraction were obtained.Comparisons with the distribution of marker enzymes indicate that NADxylitol dehydrogenase is weakly bound to the outer membrane or is present between the inner and outer membranes, or both, whereas NADP-xylitol dehydrogenase appears to be located in the matrix confined by the inner membrane or bound to the inner membrane.The possible implications of the compartmentalization of these enzymes of the glucuronate-xylulose cycle are discussed.