The oxidation of l-lactate by liver mitochondria

• Published in: Archives of biochemistry and biophysics Vol. 152; no. 1; pp. 92 - 104
• Main Authors: Skilleter, David N., Kun, Ernest
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.1972
• Subjects: Acetoacetates - metabolism; Adenosine Diphosphate - pharmacology; Aerobiosis; Animals; Carbon Dioxide - biosynthesis; Carbon Isotopes; Cytoplasm - enzymology; Digitalis Glycosides; Dinitrophenols - pharmacology; Electrophoresis, Disc; Kinetics; L-Lactate Dehydrogenase - pharmacology; Lactates - metabolism; Liver - enzymology; Male; Mitochondria, Liver - drug effects; Mitochondria, Liver - enzymology; Mitochondria, Liver - metabolism; NAD - pharmacology; Oxygen Consumption - drug effects; Pyruvates - biosynthesis; Rats; Saponins; Spirostans; Surface-Active Agents
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/0003-9861(72)90197-X

A single NAD +-dependent LDH was found in liver mitochondria, localized in the intermembrane space. Maximal aerobic oxidation of l-lactate requires externally added NAD +. Apparent K m for NAD + is the same for the aerobic oxidation of l-lactate by mitochondria, as for the oxidation of l-lactate by NAD + in the presence of mitochondrial LDH. Mitochondrial LDH contains bound NAD + which remains associated with the enzyme protein during acrylamide gel electrophoresis. Dismutation between l-lactate and acetoacetate by mitochondria is greatly stimulated by NAD + and this reaction is inhibited by DNP, while dismutation between pyruvate and acetoacetate is not. Results are interpreted in terms of a possible mitochondrial path of l-lactate oxidation. This process may involve an energy-dependent transfer of reducing equivalents between l-lactate + LDH-bound NAD +(H) and enzyme systems of the inner membrane (and matrix).