Two closely related pathways of nicotine catabolism in Arthrobacter nicotinovorans and Nocardioides sp. strain JS614
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S H O R T CO M MU N I C A T I O N
Two closely related pathways of nicotine catabolism in Arthrobacter nicotinovorans and Nocardioides sp. strain JS614 Petra Ganas · Paula Sachelaru · Marius Mihasan · Gabor L. Igloi · Roderich Brandsch
Received: 24 May 2007 / Revised: 16 November 2007 / Accepted: 26 November 2007 / Published online: 11 December 2007 © Springer-Verlag 2007
Abstract A virtually identical nicotine catabolic pathway including the heterotrimeric molybdenum enzyme nicotine and 6-hydroxy-pseudo-oxynicotine dehydrogenase, 6hydroxy-L-nicotine oxidase, 2,6-dihydroxy-pseudo-oxynicotine hydrolase, and 2,6-dihydroxypyridine hydroxylase have been identiWed in A. nicotinovorans and Nocardioides sp. JS614. Enzymes catalyzing the same reactions and similar protein antigens were detected in the extracts of the two microorganisms. Nicotine blue and methylamine, two end products of nicotine catabolism were detected in the growth medium of both bacterial species. Nicotine catabolic genes are clustered on pAO1 in A. nicotinovorans, but located chromosomally in Nocardioides sp. JS614. Keywords Nicotine catabolism · Arthrobacter nicotinovorans · Nocardioides sp. JS614 · Catabolic plasmid pAO1 · Horizontal gene transfer
Communicated by Erko Stackebrandt. P. Ganas · P. Sachelaru · R. Brandsch Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Biology, Albert-Ludwigs-University Freiburg, Hermann Herder Str. 7, 79104 Freiburg, Germany M. Mihasan Department of Experimental Biology, Alexandru-Ioan-Cuza-University Iasi, Bd. Carol I 20 A, 700505 Iasi, Romania G. L. Igloi Institute of Biology III, Albert-Ludwigs-University Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany
Introduction Nicotine catabolism by Arthrobacter nicotinovorans has been studied in some detail (for a review see Brandsch 2006). In this Gram-positive soil bacterium the genes of the pathway (the nic-genes) are clustered on the 165-kb plasmid pAO1 (Igloi and Brandsch 2003). A schematic representation of the individual steps of the pathway (Fig. 1a) shows that after the initial hydroxylation of the pyridine ring by the heterotrimeric molybdenum enzyme nicotine dehydrogenase (NDH) (nicotine:acceptor oxidoreductase) (Grether-Beck et al. 1994; Andreesen and Fetzner 2002), the pyrrolidine ring of nicotine is oxidized by the Xavoprotein 6-hydroxy-L-nicotine oxidase (6HLNO) with the formation of 6-hydroxy-pseudo-oxynicotine (“ketone”) (Decker and Dai 1967). A second hydroxylation of the pyridine ring is performed by an NDH-related enzyme, ketone dehydrogenase (KDH) (6-hydroxy-pseudo-oxynicotine:acceptor oxydoreductase) (Sachelaru et al. 2006), with subsequent cleavage of the -N-methylaminobutyrate side chain of 2,6-dihydroxy-pseudo-oxynicotine by 2,6-dihydroxy-pseudo-oxynicotine hydrolase (PONH) (Sachelaru et al. 2005) yielding 2,6-dihydroxypyridine. A further hydroxylation by 2,6-dihydroxypyridine hydroxylase (DHPH) (Baitsch et al. 2001) gives trihydroxypyridine that spontaneously forms nicotine blue (Knackmuss and Beckmann
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