title: Absence of NADH channeling in coupled reaction of mitochondrial malate dehydrogenase and complex I in alamethicin-permeabilized rat liver mitochondria.
abstract: A simple in situ model of alamethicin-permeabilized isolated rat liver mitochondria was used to investigate the channeling of NADH between mitochondrial malate dehydrogenase (MDH) and NADH:ubiquinone oxidoreductase (complex I). Alamethicin-induced pores in the mitochondrial inner membrane allow effective transport of low molecular mass components such as NAD+/NADH but not soluble proteins. Permeabilized mitochondria demonstrate high rates of respiration in the presence of malate/glutamate and NAD+ due to coupled reaction between MDH and complex I. In the presence of pyruvate and lactate dehydrogenase, an extramitochondrial competitive NADH utilizing system, respiration of permeabilized mitochondria with malate/glutamate and NAD+ was completely abolished. These data are in agreement with the free diffusion of NADH and do not support the suggestion of direct channeling of NADH from MDH to complex I.
authors.affiliation: Molecular Biology Division (151-S), VA Medical Center, San Francisco, CA 94121, USA. s2shak@post.tau.ac.il
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Kotlyar
authors.forename: Elena
authors.initials: E
authors.lastname: Maklashina
authors.forename: Gary
authors.initials: G
authors.lastname: Cecchini
mesh_terms: D000408:Alamethicin / Q000494:pharmacology*; D000818:Animals; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology; D002463:Cell Membrane Permeability / Q000187:drug effects; D042967:Electron Transport Complex I / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology* / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D014475:Uncoupling Agents / Q000494:pharmacology*
chemical_list: D005971:Glutamates; D008293:Malates; D014475:Uncoupling Agents; D009243:NAD; D000408:Alamethicin; D019289:Pyruvic Acid; D008291:Malate Dehydrogenase; D042967:Electron Transport Complex I