SPECTROSCOPIC STUDY OF HYDROXYPROLINE TRANSPORT IN RAT-KIDNEY MITOCHONDRIA

Hydroxyproline uptake by rat kidney mitochondria is here first shown b y monitoring the reduction of the intramitochondrial pyridine nucleoti des which occurs as a result of metabolism of imported hydroxyproline via hydroxyproline oxidase and 3-hydroxy-pyrroline-5-carboxylate dehyd rogenase. Widely used criteria for demonstrating the occurrence of car rier-mediated transport were applied to this process. Hydroxyproline u ptake shows saturation features (Km and Vmax values, measured at 20 de grees C and at pH 7.20, were found to be about 1.4 mM and 5 nmoles/min x mg mitochondrial protein, respectively) and proves to be inhibited by the impermeable compound phenylsuccinate, but insensitive to extern ally added methylglutamate. Difference found in the Km and Vmax values , a different inhibitor sensitivity and the failure of hydroxyproline to cause efflux of glutamate from the mitochondria show that hydroxypr oline enters mitochondria by means of a translocator different from th ose which transport proline. (C) 1944 Academic Press, Inc.