An assay has been developed in which the activity of an ubiquinol oxidase from Escherichia coli, cytochrome bo(3) (cbo(3)), is determined as a function of the hydrophobic substrate ubiquinol-10 (UQ-10) in tethered bilayer lipid membranes (tBLMs). UQ-10 was added in situ, while the enzyme activity and the UQ-10 concentration in the membrane have been determined by cyclic voltammetry. Cbo(3) is i...

The suitability of ubiquinol(1) and duroquinol as pulse reductants for initiating respirationdriven proton translocation by aerobic ox heart mitochondria was investigated. At 25 degrees C the V(max.) for oxidation was close to 280nmol of quinol oxidized/min per mg of protein, and the K(m) values were 8mum for ubiquinol(1) and 28mum for duroquinol. Pulses of ubiquinol(1) and duroquinol were rapi...

The cytochrome bc(1) complex is a dimeric enzyme that links electron transfer from ubiquinol to cytochrome c by a protonmotive Q cycle mechanism in which ubiquinol is oxidized at one center in the enzyme, referred to as center P, and ubiquinone is re-reduced at a second center, referred to as center N. To understand better the mechanism of ubiquinol oxidation, we have examined the interaction o...

Bifurcated electron flow to high potential "Rieske" iron-sulfur cluster and low potential heme b(L) is crucial for respiratory energy conservation by the cytochrome bc(1) complex. The chemistry of ubiquinol oxidation has to ensure the thermodynamically unfavorable electron transfer to heme b(L). To resolve a central controversy about the number of ubiquinol molecules involved in this reaction, ...

Coenzyme Q10 (CoQ10) is a ubiquitous nutrient in human cells where it is essential for mitrochondrial energy production. CoQ10 exists in both an oxidized (ubiquinone) and reduced form (ubiquinol), with ubiquinol being the bioactive form. In addition to its use in cellular ATP production ubiquinol acts as a powerful lipid-soluble antioxidant that protects lipid membranes and lipoproteins from ox...

The cytochrome bc1 complex is a dimeric enzyme of the inner mitochondrial membrane that links electron transfer from ubiquinol to cytochrome c by a protonmotive Q cycle mechanism in which ubiquinol is oxidized at one center in the enzyme, referred to as center P, and ubiquinone is rereduced at a second center, referred to as center N. To better understand the mechanism of ubiquinol oxidation, w...

A refinement of the protonmotive Q cycle mechanism is proposed in which oxidation of ubiquinol is a concerted reaction and occurs by an alternating, half-of-the-sites mechanism. A concerted mechanism of ubiquinol oxidation is inferred from the finding that there is reciprocal control between the high potential and low potential redox components involved in ubiquinol oxidation. The potential of ...

Coenzyme Q10 (CoQ10) provides the energy for vital cellular functions and is known to act as an antioxidant. We conducted an open label study to examine the clinical effects of supplementation of the reduced form of CoQ10, ubiquinol, in addition to conventional glucose-lowering agents in patients with type 2 diabetes. Nine subjects (3 males and 6 females) with type 2 diabetes and receiving conv...