3NG7

Complex of dithionite-reduced 6-hydroxy-L-nicotine oxidase with substrate bound at active site and inhibitor at exit cavity

Summary for 3NG7

• Entry DOI: 10.2210/pdb3ng7/pdb
• Related: 3K7M 3K7Q 3K7T
• Descriptor: 6-hydroxy-L-nicotine oxidase, 5-[(2S)-1-methylpyrrolidin-2-yl]pyridin-2-ol, FLAVIN-ADENINE DINUCLEOTIDE, ... (6 entities in total)
• Functional Keywords: enantiomeric substrate-inhibitor, flavoenzymes, nicotine degradation, oxidase, oxidoreductase, oxidoreductase-oxidoreductase inhibitor complex, oxidoreductase/oxidoreductase inhibitor
• Biological source: Arthrobacter nicotinovorans
• Total number of polymer chains: 1
• Total formula weight: 49030.00

Authors

Kachalova, G.S.,Bartunik, H.D. (deposition date: 2010-06-11, release date: 2011-03-16, Last modification date: 2023-11-01)

Primary citation

Kachalova, G.,Decker, K.,Holt, A.,Bartunik, H.D.
Crystallographic snapshots of the complete reaction cycle of nicotine degradation by an amine oxidase of the monoamine oxidase (MAO) family
Proc.Natl.Acad.Sci.USA, 108:4800-4805, 2011

PubMed Abstract: FAD-linked oxidases constitute a class of enzymes which catalyze dehydrogenation as a fundamental biochemical reaction, followed by reoxidation of reduced flavin. Here, we present high-resolution crystal structures showing the flavoenzyme 6-hydroxy-l-nicotine oxidase in action. This enzyme was trapped during catalytic degradation of the native substrate in a sequence of discrete reaction states corresponding to the substrate-reduced enzyme, a complex of the enzyme with the intermediate enamine product and formation of the final aminoketone product. The inactive d-stereoisomer binds in mirror symmetry with respect to the catalytic axis, revealing absolute stereospecificity of hydrogen transfer to the flavin. The structural data suggest deprotonation of the substrate when bound at the active site, an overall binary complex mechanism and oxidation by direct hydride transfer. The amine nitrogen has a critical role in the dehydrogenation step and may activate carbocation formation at the α-carbon via delocalization from the lone pair to σ* C(α)-H. Enzymatically assisted hydrolysis of the intermediate product occurs at a remote (P site) cavity. Substrate entry and product exit follow different paths. Structural and kinetic data suggest that substrate can also bind to the reduced enzyme, associated with slower reoxidation as compared to the rate of reoxidation of free enzyme. The results are of general relevance for the mechanisms of flavin amine oxidases.

PubMed: 21383134
DOI: 10.1073/pnas.1016684108

Experimental method

X-RAY DIFFRACTION (1.95 Å)