Dimethylsulfoxide Reductase: Insight into the Mechanisms of the Catalytic Reactions from Structural and Spectroscopic Studies

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1 p.

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Journal of Inorganic Biochemistry

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doi: 10.1016/S0162-0134(99)00064-1


Dimethysulfoxide (DMSO) reductase from the photosynthetic bacteria Rhodobacter sp. is a molybdenum containing enzyme belonging to the structurally and catalytically diverse family of non-nitrogenase molybdenum cofactor (Moco) enzymes. These enzymes are characterised by containing one or two organic cofactor moieties based around a common pterin, "molybdopterin". The pterin(s) ligate the Mo ion via an ene-dithiolate functionality. An entirely analogous family of enzymes containing tungsten has more recently been characterised and contains the same pterin moiety as if found in the molybdenum enyzmes. However, whilst the ranges of catalytic reactions of Mo and W enzymes overlap considerably, direct substitution of one metal for another in a given polypeptide generally results in loss of activity and in marked changes in spectroscopic and electrochemical properties.

While many Mo enzymes have been keenly studied because of their biomedical, agricultural or environmental importance, DMSO reductase is of particular interest as, uniquely, it contains Moco and no other chromophoric redox centres. Thus the DMSO reductases from Rh. capsulatusand Rh. sphaeroides have been proven amendable to study using a number of spectroscopic techniques (EPR, MCD, RR). More recently, these enzymes have been subjected to structural analysis by X-ray crystallography and EXAFS by a number of investigators. Despite the wealth of available information, however, a consensus has not been reached as to the mechanisms of the catalytic reactions, the structures of the Mo sites in active, resting states or of the nature of the myriad species of the enzymes observable by spectroscopy.

Here we present new structural and spectroscopic data which follow on from earlier work from our laboratory [1,2,3,4]. We discuss the structural and mechanistic implications of this work.

[1] Bennett, B. et al. Eur. J. Biochem. 1994, 225, 321-331.
[2] McAlpine, A. S. et al. J. Biol. Inorg. Chem. 1997, 2, 690-701.
[3] Baugh, P.E. et al. J. Biol. Inorg. Chem. 1997, 2, 634-643.
[4] McAlpine, A. S. et al. J. Mol. Biol. 1998, 275, 613-623.


Journal of Inorganic Biochemistry, Vol. 74 (April 30, 1999): 76. DOI.

Brian Bennett was affiliated with the CCLRC Daresbury Laboratory at the time of publication.