A NAD(P)H-nicotine blue oxidoreductase is part of the nicotine regulon and may protect Arthrobacter nicotinovorans from oxidative stress during nicotine catabolism

Institute for Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research, Institute of Organic Chemistry and Biochemistry, Albert-Ludwigs University, Freiburg, Germany, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA, Department of Molecular and Experimental Biology, Alexandru Ioan Cuza University, Iasi, Romania

^* To whom correspondence should be addressed. Email: roderich.brandsch{at}biochemie.uni-freiburg.de.

	Abstract

A NAD(P)H-nicotine blue (quinone) oxidoreductase was discovered as member of the nicotine catabolic pathway of Arthrobacter nicotinovorans. Transcriptional analysis and electromobility shift assays showed that the enzyme gene was expressed in a nicotine-dependent manner under the control of the transcriptional activator PmfR and thus was part of the nicotine regulon of A. nicotinovorans. The FMN-containing enzyme uses NADH and, with lower efficiency NADPH, to reduce, by a two-electron transfer, nicotine blue to the nicotine blue leuco form (hydroquinone). Besides nicotine blue several other quinones were reduced by the enzyme. The NAD(P)H-nicotine blue oxidoreductase may prevent intracellular one-electron reductions of nicotine blue which may lead to semiquinone radicals and potentially toxic reactive oxygen species.