Open AccessSulfite Binding to a Flavodehydrogenase, Cytochrome b 2 from Baker's Yeast
Author(s) -
LEDERER Florence
Publication year - 1978
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1978.tb12465.x
Subject(s) - chemistry , sulfite , semiquinone , flavin group , reactivity (psychology) , flavoprotein , electron acceptor , photochemistry , stereochemistry , sulfite oxidase , chromophore , enzyme , biochemistry , medicine , alternative medicine , pathology , quinone
Baker's yeast l ‐lactate dehydrogenase (flavocytochrome b 2 ) is a typical flavodehydrogenase, in that it accepts two electrons from the substrate but has a monoelectronic acceptor. Yet it forms a red semiquinone [Capeillère Blandin et al. Eur. J. Biochem. 54 , 549‐566 (1975)] and it is shown in this paper that it forms a reversible covalent complex with sulfite ( K d = 1.4 μM). This complex can be observed by difference spectroscopy and provides a convenient tool for visualizing the flavin chromophore, usually hidden behind the intense heme absorbance. A number of anions ( d ‐lactate, oxalate and pyruvate) are inhibitors of the enzymatic reaction and induce spectral perturbations of the flavin spectrum. It is concluded that probably two positive charges exist at the active site: one which stabilizes the red semiquinone and one which attracts organic anions and sulfite. It is also concluded that the correlation between reactivity with sulfite and reactivity with oxygen among flavo‐proteins may not be as general as previously proposed [Massey et al. J. Biol. Chem. 244 , 3999‐4006 (1969)].