ISSN:
1432-1327
Keywords:
Key words Molybdenum oxotransferase
;
Resonance Raman
;
Catalytic mechanism
;
18O labeling
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Recent studies of human sulfite oxidase and Rhodobacter sphaeroides DMSO reductase have demonstrated the ability of resonance Raman to probe in detail the coordination environment of the Mo active sites in oxotransferases via Mo=O, Mo-S(dithiolene), Mo-S(Cys) or Mo-O(Ser), dithiolene chelate ring and bound substrate vibrations. Furthermore, the ability to monitor the catalytically exchangeable oxo group via isotopic labeling affords direct mechanistic information and structures for the catalytically competent Mo(IV) and Mo(VI) species. The results clearly demonstrate that sulfite oxidase cycles between cis–di-oxo-Mo(VI) and mono-oxo-Mo(IV) states during catalytic turnover, whereas DMSO reductase cycles between mono-oxo-Mo(VI) and des-oxo-Mo(IV) states. In the case of DMSO reductase, 18O-labeling experiments have provided the first direct evidence for an oxygen atom transfer mechanism involving an Mo=O species. Of particular importance is that the active-site structures and detailed mechanism of DMSO reductase in solution, as determined by resonance Raman spectroscopy, are quite different to those reported or deduced in the three X-ray crystallographic studies of DMSO reductases from Rhodobacter species.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050198
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