Identification and characterization of a novel class of self-sufficient cytochrome P450 hydroxylase involved in cyclohexanecarboxylate degradation in Paraburkholderia terrae strain KU-64.

Cytochrome P450 monooxygenases play important roles in metabolism. Here, we report the identification and biochemical characterization of P450CHC, a novel self-sufficient cytochrome P450, from cyclohexanecarboxylate-degrading Paraburkholderia terrae KU-64. P450CHC was found to comprise a [2Fe-2S] ferredoxin domain, NAD(P)H-dependent FAD-containing reductase domain, FCD domain, and cytochrome P450 domain (in that order from the N terminus). Reverse transcription-polymerase chain reaction results indicated that the P450CHC-encoding chcA gene was inducible by cyclohexanecarboxylate. chcA overexpression in Escherichia coli and recombinant protein purification enabled functional characterization of P450CHC as a catalytically self-sufficient cytochrome P450 that hydroxylates cyclohexanecarboxylate. Kinetic analysis indicated that P450CHC largely preferred NADH (Km = 0.011 m m) over NADPH (Km = 0.21 m m). The Kd, Km, and kcat values for cyclohexanecarboxylate were 0.083 m m, 0.084 m m, and 15.9 s-1, respectively. The genetic and biochemical analyses indicated that the physiological role of P450CHC is initial hydroxylation in the cyclohexanecarboxylate degradation pathway.