Jerusalem artichoke mitochondria can export reducing equivalents in the form of malate as a result of D-lactate uptake and metabolism

de Bari, L.; Valenti, D.; Pizzuto, R.; Paventi, G.; Atlante, A.; Passarella, S.

Biochemical and Biophysical Research Communications 335(4): 1224-1230

2005


ISSN/ISBN: 0006-291X
PMID: 16129093
DOI: 10.1016/j.bbrc.2005.08.022
Accession: 004446090

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Abstract
We found that as a result of D-lactate uptake and metabolism by Jerusalem artichoke mitochondria, reducing equivalents were exported from the mitochondrial matrix to the exterior in the form of malate. The rate of malate efflux, as measured photometrically using NADP+ and malic enzyme, depended on the rate of transport across the mitochondrial membrane. It showed saturation characteristics (Km=5 mM; Vmax=9 nmol/min mg of mitochondrial protein) and was inhibited by non-penetrant compounds. We conclude that reducing equivalent export from mitochondria is due to the occurrence of a putative d-lactate/malate antiporter which differs from other mitochondrial carriers, as shown by the different inhibitor sensitivity.