Cytochrome c-dependent methacrylate reductase from Geobacter sulfurreducens AM-1

Geobacter sulfurreducens AM-1 can use methacrylate as a terminal electron a cceptor for anaerobic respiration. In this paper, we report on the purifica tion and properties of the periplasmic methacrylate reductase, and show tha t the enzyme is dependent on the presence of a periplasmic cytochrome c (ap parent K-m = 0.12 mu M). The methacrylate reductase was found to be compose d of only one polypeptide with an apparent molecular mass of 50 kDa and to contain, bound tightly but not covalently, 1 mol of FAD per mel. The N-term inal, amino acid sequence showed sequence similarity to a periplasmic fumar ate reductase from Shewanella putrefaciens. However, methacrylate reductase did not catalyze the reduction of fumarate. The periplasmic cytochrome c, which was also purified, had an apparent molecular mass of 30 kDa and conta ined approximate to 4 mol of heme mol(-1). Cells of G. sulfurreducens AM-1 grown on acetate and methacrylate as; an energy source were found to contai n all the enzymes required for the oxidation of acetate to CO2 via the citr ic acid cycle.