Biochemical and Biophysical Research Communications 1994-07-15

Spectroscopic study of hydroxyproline transport in rat kidney mitochondria.

A Atlante, S Passarella, E Quagliariello

Index: Biochem. Biophys. Res. Commun. 202(1) , 58-64, (1994)

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Abstract

Hydroxyproline uptake by rat kidney mitochondria is here first shown by monitoring the reduction of the intramitochondrial pyridine nucleotides which occurs as a result of metabolism of imported hydroxyproline via hydroxyproline oxidase and 3-hydroxy-pyrroline-5-carboxylate dehydrogenase. Widely used criteria for demonstrating the occurrence of carrier-mediated transport were applied to this process. Hydroxyproline uptake shows saturation features (Km and Vmax values, measured at 20 degrees 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 externally 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 hydroxyproline enters mitochondria by means of a translocator different from those which transport proline.