Aldehyde: ferredoxin oxidoreductase

A few representative Mo enzymes are listed in Table 18-C-6. Note that most have very high molecular weights, and this has delayed structure determinations. In the case of DMSO-reductase, however, the lower molecular weight has made possible a structure determination. The Mo site is found to be as shown in 18-C-XXVII. In a tungsten-containing enzyme, ferredoxin aldehyde oxidoreductase, the metal site is as shown in 18-C-XXVIII. 

Antitumor drugs cisplatin as, history, 37 175-179 platinum compounds future studies, 37 206-208 resistance to, 37 192-193 second-generation, 37 178 Antiviral agents, 36 37-38 AOR, see Aldehyde oxidoreductase Aphanothece sacrum, ferredoxins, amino acid sequence, 38 225-227 Apo-calcylin, 46 455 Apo-caldodulin, 46 449-450 Apoenzyme, 22 424 Apoferritin biosynthesis, 36 457 cystalline iron core, 36 423 Fe(III)distribution, 36 458-459 Fe(II) sequestration, 36 463-464 ferroxidase centers, 36 457-458 iron core reconstruction in shell, 36 457 mineralization, 36 25 Mdssbauer spectra, 36 459-460 optical absorbance spectra, 36 418-419 subunit conformation and quaternary structure, 36 470-471... 

Figure 16-31 (A) Structure of molybdopterin cytosine dinucleotide complexed with an atom of molybdenum. (B) Stereoscopic ribbon drawing of the structure of one subunit of the xanthine oxidase-related aldehyde oxidoreductase from Desulfo-vibrio gigas. Each 907-residue subunit of the homodimeric protein contains two Fe2S2 clusters visible at the top and the molybdenum-molybdopterin coenzyme buried in the center. (C) Alpha-carbon plot of portions of the protein surrounding the molybdenum-molybdopterin cytosine dinucleotide and (at the top) the two plant-ferredoxin-like Fe2S2 clusters. Each of these is held by a separate structural domain of the protein. Two additional domains bind the molybdopterin coenzyme and there is also an intermediate connecting domain. In xanthine oxidase the latter presumably has the FAD binding site which is lacking in the D. gigas enzyme. From Romao et al.633 Courtesy of R. Huber.

The aldehyde ferredoxin oxidoreductase from the hyperthermophile Pyrococcus furiosus was the first molybdopterin-dependent enzyme for which a three-dimensional structure became available.683,684 The tungstoenzyme resembles that of the related molybdo-enzyme (Fig. 16-31). A similar ferredoxin-dependent enzyme reduces glyceraldehyde-3-phosphate.685 Another member of the tungstoenzyme aldehyde oxidoreductase family is carboxylic acid reductase, an enzyme found in certain acetogenic clostridia. It is able to use reduced ferredoxin to convert unactivated carboxylic acids into aldehydes, even though E° for the acetaldehyde/acetate couple is -0.58 V.686... 

Mukund S, MWW Adams (1991) The novel tungsten-iron-sulfur protein of the hyperthermophilic archaebacterium, Pyrococcus furiosus, is an aldehyde ferredoxin oxidoreductase. J Biol Chem 266 14208-14216. 

Chan, M.K., S. Mukund, A. Kletzin, M.W. Adams, and D.C. Rees. 1995. Structure of a hyperthermophilic tungstopterin enzyme, aldehyde ferredoxin oxidoreductase. Science 267 1463-1469. 

Pyrimidinethione complexes, osmium, 37 296 Pyriminethionate, as bridging ligands in platinum dimers, 40 202-205 Pyrochlores, 17 108 Pyrococcus furiosus, 38 344-383 aldehyde ferredoxin oxidoreductase, 38 374-381... 

Aldehyde ferredoxin oxidoreductase Benzene-1,2-dithiolate Biotin sulfoxide reductase Density functional theory... 

The crystal structure of aldehyde ferredoxin oxidoreductase (AOR) from the hyperthermophile Pyrococcus furiosus was the first of any molybdenum or tungsten enzyme (excepting nitrogenase) (42). The AOR was adopted as the parent name for the family of tungsten enzymes. The structure of formaldehyde ferredoxin oxidoreductase (FOR) has recently been solved (44). 

Although less prominent than their molybdenum counterparts, several tungsten-containing enzymes have been isolated and characterized (2, 10, 20, 23, 24a). A notable aspect of the biochemical role of these enzymes is that many occur in hyperthermophilic archea that live at temperatures of 100 °C. The known tungsten enzymes can be classified into three functional and phylogen-etically distinct families, the representative members being aldehyde ferredoxin oxidoreductase formaldehyde ferredoxin oxidoreductase and gyceraldehyde-3-phosphate ferredoxin oxidoreductase (23). 

FDH = Formate dehydrogenase CAR = Carboxyhc acid reductase FMDH = Formylmethanofuran dehydrogenase MFR = Methanofuran AOR = Aldehyde ferredoxin oxi-doreductase MPT = Molybdopterin Fdox = Oxidized ferredoxin Fdred = Reduced ferredoxin FOR = Formaldehyde ferredoxin oxidoreductase EXAFS = X-ray absorption edge fine structure kDa = Kilodaltons EPR = Electron paramagnetic resonance. 

As stated, the RTF is the inactive form of aldehyde ferredoxin oxidoreductase (AOR). The active AOR enzyme may be isolated by rapid purification under anaerobic conditions using buffer containing dithio-threitol and glycerol (282). AOR catalyzes Eq. (28) and is postulated to contain a W—SH group not present in the RTF. 

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