Periplasmic methacrylate reductase activity in Wolinella succinogenes

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.