Azotobacter, transhydrogenase

Pseudomonas and Azotobacter transhydrogenases was provided by Cohen and Kaplan (17) and by van den Broek et al. [19), respectively, who showed that inactivation by heat treatment could be reversed by addition of FAD. FAD could not be replaced by FMN. Reduction of the enzyme with either NADH or NADPH largely increased the heat sensitivity, whereas oxidized nicotinamide nucleotides or FAD had the opposite effect (17, 19). The number of flavins per 50,000-dalton molecular weight was calculated to be 0.58 to 1.1 (17). 

The reaction mechanism of the Pseudomonas and Azotobacter transhydrogenases has been extensively investigated. Studies of the steady-state kinetics of Pseudomonas transhydrogenase by Cohen 27) and by Cohen... 

Middleditch, L. E., Chung, A. E. Pyridine nucleotide transhydrogenase from Azotobacter vinelandii cells Stereospecificity of hydrogen transfer. Arch. Biochem. Biophys 146, 449—453 (1971). 

Youssef NN, Hammond D (1971) The fine structure of the developmental stages of the microsporidian Nosema apis Zander. Tissue Cell 3 283-294 Yu Y, Samuelson J (1994) Primary structure of an Entamoeba histolytica nicotinamide nucleotide transhydrogenase. Mol Biochem Parasitol 68 323-328 Zheng L, Cash VL, Hint DH, Dean DR (1998) Assembly of iron-sulfur clusters. Identification of an iscSUA-hscBA-fdx gene cluster from Azotobacter vinelandii. J Biol Chem 273 13264-13272... 

In addition to transfer of hydrogen between various nicotinamide nucleotides, the transhydrogenases from Pseudomonas 17), spinach 11, 13), and Azotobacter 9, 19) also catalyze a diaphorase reaction, using either NADH or NADPH plus an artificial acceptor, e.g., potassium fer-ricyanide or dichlorophenolindophenol. As expected, 2 -AMP stimulates the NADH-linked diaphorase reaction catalyzed by the Pseudomonas enzyme 17). 

Thioredoxin reductase (EXl 1.6.4.5) has been purified from E. coli (8, 36), yeast (6, 7, 66, iP75), and rat liver supernatant (202, 2 ). Only the enzyme from E. coli has been extensively characterized, and it will be discussed exclusively below. The similarity of the transhydrogenase from Azotobacter vinelandii to thioredoxin reductase has been noted (281). 

Azotobacter agile, transhydrogenase of, 54 Azotobacter chroococcum nitrite reductase of, 275, 276-277 transhydrogenase of, 54 Azotobacter vinelandii NADH dehydrogenase of, 221... 

Jeun YS, Kim MD, Park YC, Lee TH, Yoo MS, Ryu YW, Seo JH. (2003). Expression of Azotobacter vinelandii soluble transhydrogenase perturbs xylose reductase-mediated conversion of xylose to xylitol by recombinant Saccharomyces cerevisiae. J Mol Catal B-Enzym, 26, 251-256. 

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