ABSTRACT
The results of protein crystallographic investigations, linked to spectroscopic studies of the metal centers of the molybdenum oxotransferases and tungstoenzymes (see Sec. 2 ), have greatly advanced our understanding of the nature of the coordination sphere of molybdenum in oxotransferase enzymes and tungsten in tungstoenzymes. The structural results have led to a broad classification of the molybdenum oxo transferases (as shown in Fig. 4). For details of the coordination sphere of molybde num in the oxotransferases, the reader is specifically referred to DMSO reductase, Sec. 2.3.1.1/Fig. 11; TMAO reductase, Sec. 2.3.1.2/Fig. 14; formate dehydrogenase H, Sec. 2.3.1.3/Fig. 16; dissimilatory nitrate reductase, Sec. 2.3.1.4./ Fig. 18; sulfite oxi dase, Sec. 2.3.2./Fig. 20; aldehyde oxidase, Sec. 2.3.3.l./Fig. 2 2 ; CO hydrogenase, Sec. 2.3.3.2/Fig. 24. The tungstoenzymes, aldehyde oxidoreductase and formaldehyde ferredoxin oxidoreductase, are described in Sec. 2.4 and the nature of tungsten center of the former is shown in Fig. 27.
