Desulfonation of propanesulfonic acid by Comamonas acidovorans strain P53:evidence for an alkanesulfonate sulfonatase and an atypical sulfite dehydrogenase

Evidence is presented for the presence in propanesulfonate-grown Comamonas acidovorans strain P53 of a cytoplasmically located sulfonatase that does n ot sediment at 100,000 x g. This enzyme catalysed the sulfonate-dependent o xidation of NADH or NADPH, indicating a monooxygenase that effects the addi tion of molecular oxygen to C-3-C-6 1-alkanesulfonates. Enzyme activity was proportional to protein concentration only above approximately 2 mg cytopl asmic fraction protein ml(-1), suggesting that the sulfonatase is a multico mponent enzyme, possibly comparable with methanesulfonate monooxygenase. En zyme activity was strongly inhibited by divalent metal-chelating agents, bu t was insensitive to cyanide and azide. Sulfite released from sulfonates by Comamonas acidovorans was oxidized by an unusual sulfite dehydrogenase. Th is was purified approximately 230-fold and was shown to have a molecular ma ss of 74.4 kDa, comprising two or more subunits. The enzyme activity was sp ecific in vitro for ferricyanide as an electron acceptor and, unlike other bacterial sulfite dehydrogenases, did not contain native cytochrome c or re duce added cytochrome c. It was a basic protein, insensitive to chloride an d sulfate, and exhibited a K-m for sulfite of approximately 45 mu M.