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Updated: Aug 14, 2026

Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles
Published on: December 31, 2019
Metabolite transport in rat kidney mitochondria: ornithine/phosphate translocator
S Passarella1, A Atlante, E Quagliariello
1Dipartimento di Biochimica e Biologia Molecolare, Università di Bari, Italy.
Abstract:
Ornithine 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 ornithine via ornithine aminotransferase and 1-pyrroline-carboxylate dehydrogenase. Ornithine uptake shows saturation features (Km and Vmax values, measured at 20 degrees C and at pH 7.20, were found to be about 0.85 mM and 23 nmoles/min x mg protein, respectively) and proves to be inhibited by D-ornithine, inorganic phosphate, praseodimium chloride and mersalyl. Neither malate nor glutamate, but phosphate was found to exchange with ornithine. Phosphate efflux caused by externally added ornithine was shown both as revealed by a c colorimetric assay and as continuously monitored by measuring extramitochondrial reduction of NAD+ in the presence of glyceraldehyde-3-phosphate, glyceraldehyde-3-phosphate dehydrogenase, ADP and 3-phosphoglycerate kinase. The role of ornithine carrier in kidney metabolism will also be discussed.
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