The cell homogenate and the soluble cell fraction of Wolinella succinogenes
grown with formate and fumarate catalyzed the oxidation of benzyl viologen
radical by methacrylate [apparent K-m=0.23 mM, V-max =1.0 U (mg cell prote
in)(-1)] or acrylate [apparent K-m=0.50 mM, V-max=0.77 U (mg cell protein)(
-1)]. Crotonate did not serve as an oxidant, A mutant of W. succinogenes la
cking the fccABC operon was unable to catalyze methacrylate or acrylate red
uction. In contrast, the inactivation of fcc-C alone had no effect on these
activities. Methacrylate reduction by benzyl viologen radical was not cata
lyzed by fumarate reductase isolated from the membrane of W. succinogenes.
Cells grown with formate and fumarate did not catalyze methacrylate reducti
on by formate, and W. succinogenes did not grow with formate and methacryla
te as catabolic substrates. The results suggest that the reduction of metha
crylate or acrylate by benzyl viologen radical is most likely catalyzed eit
her by the periplasmic flavoprotein FccA or by a complex consisting of FccA
and the predicted c-type cytochrome FccB. The metabolic function of the fc
cABC operon remains unknown.