Revisiting pitfalls, problems and tentative solutions for assaying mitochondrial respiratory chain complex III in human samples.
The assessment of mitochondrial respiratory chain enzyme activity in human samples is a difficult task due to both the small amount of tissue generally available and the frequent need to perform enzyme activity measurement in crude mitochondrial fraction. This is particularly true for the measurement of complex III activity which partial deficiency can be easily overlooked. In this review, we first consider the several interfering reactions occurring when measuring this activity. We subsequently describe the use of an alkyl glycoside detergent, lauryl maltoside, to keep these interfering reactions to a very low level. Next, we quantify the effect of the detergent on the actual measurement of complex III in various human tissue samples and cells. Finally, we also demonstrate that the use of the detergent allows (i) a better detection of an inherited partial defect affecting cytochrome b, a catalytic subunit of the mitochondrial complex III, (ii) to possibly discriminate decreased complex III activity resulting from an abnormal complex III assembly (BCS1 gene mutation) from an hampered catalytic activity originating from a cytochrome b mutation. This detailed review of the problems associated with complex III assessment and of their tentative solution highlights the difficulties still encountered in the measurements of mitochondrial respiratory chain in humans.
Chretien
Dominique
D
Unité de Recherches sur les Handicaps Génétiques de l'Enfant, INSERM U393, Hôpital des Enfants-Malades, 149, rue de Sèvres, 75743 Paris Cedex 15, France.
Slama
Abdelhamid
A
Brière
Jean-Jacques
JJ
Munnich
Arnold
A
Rötig
Agnès
A
Rustin
Pierre
P
D004579:Electron Transport; D014450:Electron Transport Complex III / Q000032:analysis* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D010084:Oxidation-Reduction
D014450:Electron Transport Complex III