Reduction of ubiquinone by lipoamide dehydrogenase : An antioxidant regenerating pathway

• Lipoamide dehydrogenase belongs to a family of pyridine nucleotide disulfide oxidoreductases and is ubiquitous in aerobic organisms. This enzyme also reduces ubiquinone (the only endogenously synthesized lipid-soluble antioxidant) to ubiquinol, the form in which it functions as an antioxidant. The reduction of ubiquinone was linear with time and exhibited turnover numbers of 5 and 1.2 min-1 in the presence and absence of zinc, respectively. The reaction was stimulated by zinc and cadmium but not by the other divalent ions tested. The zinc/cadmium-dependent stimulation of the reaction increased rapidly and linearly up to a concentration of 0.1 mM and was even further increased at 0.5 mM. At pH 6, the activity was three times higher than at physiological pH. Alteration of the NADPH : NADP+ ratio revealed that the reaction is inhibited by higher concentrations of the oxidized cofactors. FAD reduced ubiquinone in a dose-dependent manner at a considerably lower rate, suggesting that the reduction of ubiquinone by lipoamide dehydrogenase involves the FAD moiety of the enzyme.

Subject headings

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Keyword

Antioxidants

Lipoamide dehydrogenase

Oxidative stress

Ubiquinone

Zinc

antioxidant

cadmium

dihydrolipoamide dehydrogenase

nicotinamide adenine dinucleotide phosphate

oxidoreductase

reduced nicotinamide adenine dinucleotide phosphate

article

controlled study

dose response

high performance liquid chromatography

priority journal

reduction

Animals

Cations

Divalent

Chromatography

High Pressure Liquid

Coenzymes

Flavin-Adenine Dinucleotide

Heart

Hydrogen-Ion Concentration

Kinetics

Lipid Peroxidation

NAD

NADP

Oxidation-Reduction

Swine

Publication and Content Type

ref (subject category)

art (subject category)