Catalytic properties of the mitochondrial NADH-ubiquinone oxidoreductase (complex I) and the pseudo-reversible active/inactive enzyme transition.

1. IntroductionIn the comprehensive review entitled ‘The DPNHdehydrogenase of the mitochondrial respiratory chain’written more than quarter of a century ago, theauthors stated: ‘‘Thanks to the application of sophis-ticated techniques, the characteristics of this unusualand interesting enzyme are now understood, at leastin broad terms, long-standing debates in the literaturehave been satisfactorily resolved, and the way nowseems clear for the solution of the remaining prob-lems ...’’ 1 . Five years later another scholar ofwxComplex I has pointed out that ‘‘...since no realbreakthrough in the area have occurred since 1963, itis difficult to find a fresh approach to the subject’’