ISBN: 978-83-60043-10-3 - eurobic9

J.J.G. Moura
Eurobic9, 2-6 September, 2008, Wrocław, Poland
KL30. Biological Reduction of Nitrate: Mechanistic Aspects
Departamento de Química, REQUIMTE, Faculdade de Ciências e Tecnologia, Universidade Nova De Lisboa
Campus de Caparica, 2829-516 Caparica, Portugal,
e-mail: jose.moura@dq.fct.unl.pt
New coordination sphere of Mo has been recently proposed in Nitrate reductases, mononuclear molybdenum
containing enzymes, which led to revise the currently accepted reaction mechanisms. One essential aspect is the
presence of a sulfur in the coordination sphere of Molybdenum (in addition to two MGD and a Cystein) as well
as the redox interplay of molybdenum and sulfur in the enzyme behavior. Data now available and experiments
performed on as-prepared, EPR active and inhibited forms of the enzyme, and the high quality of the diffraction
data, prompted a detailed analysis that has helped to clarify the true nature of the sixth Mo ligand. The
spectroscopic data, conducted under different experimental conditions, are combined with DFT calculations in
order to probe the enzyme mechanism. The combination of these spectroscopic studies allowed a deeper
understanding about the inhibition mechanism of periplasmic nitrate reductases. Also, EPR studies, under
turnover conditions, have helped to ascertain the nature of the turnover species. The implications of these results
are discussed also in terms of W containing enzymes (Formate dehydrogenases).
Keywords: nitrate reductases, formate dehydrogenases, molybdenum, tungsten, electron paramagnetic
resonance, X-ray crystallography, DFT.
Acknowledgement:
BIOIN, BIOPROT and X-Tal Groups at REQUIMTE, and FCT-MCTES.
References:
Periplasmic nitrate reductase revisited: a sulfur atom completes the sixth coordination of the catalytic
molybdenum. Najmudin S, González PJ, Trincão J, Coelho C, Mukhopadhyay A, Cerqueira NM, Romão CC,
Moura I, Moura JJ, Brondino CD, Romão MJ (2008) J Biol Inorg Chem. 13, 737-53.
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