Pseudomonas transhydrogenase

Sulfhydryl agents, e.g., p-hydroxymercuribenzoate, both inactivate and activate the Pseudomonas enzyme, depending on the presence of oxidized and reduced substrates, respectively (17). Inactivated protein may be reactivated by mercaptoethanol suggesting that p-hydroxymercuribenzo-ate acts on sulfhydryl groups near or at the active site. Reversible effects of sulfhydryl agents were also observed with the Chromatium enzyme (16). Proteolytic enzymes such as trypsin did not inactivate the Pseudomonas transhydrogenase (8). 

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... 

Protons, transhydrogenase and, 77-78 Protoporphyrin IX, catalase and, 366 Pseudomonas transhydrogenase function, 80... 

Hydride Transfer in NAD+- and NADP -Dependent Enzymes. The transfer of the hydride ion in redox reaction of NAD+- and NADP+-dependent enzymes can occur either to the re- or the xi-face of the pyridine ring of the coenzyme . Such stereochemistry is crucial in the characterization of these enzymes. The same enzymes from different sources can express different stereospecificities. For example, E. coli NAD(P)+ transhydrogenase expressed one form of stereospecificity whereas the Pseudomonas aeruginosa enzyme catalyzes the identical reaction with the other NAD form . 

Investigations by Colowick et al. (1) on isocitrate dehydrogenase in Pseudomonas fiuorescem led to the discovery that in the presence of extracts of these bacteria NAD could be reduced by isocitrate provided a catalytic amount of NADP was added. It was proposed that a specific enzyme, called pyridine nucleotide transhydrogenase, catalyzed the for-... 

Nicotinamide nucleotide transhydrogenase was originally discovered in Pseudomonas fluorescens. Part of the work done with these bacteria by Kaplan and co-workers (see 7) appeared later to have involved Pseudomonas aeruginosa. There is little doubt, however, that these two strains contain transhydrogenases that are closely related. Kaplan and co-workers (5) also demonstrated the presence of transhydrogenase in... 

The first demonstration of transhydrogenase activity in Pseudomonas fluoreacens by Colowick et al. (1) was carried out with a crude extract obtained from cells grown on citrate as the sole carbon source. This extract could be fractionated further by acetone precipitation followed by calcium phosphate adsorption and subsequent elution with potassium phosphate. A second acetone fractionation and calcium phosphate adsorption gave a total purification of about 200-fold. This preparation was devoid of dehydrogenase activity using glutamate, isocitrate, lactate,... 

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). 

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). 

In contrast to the transhydrogenase factor isolated from Rhodo-pseudomonas spheroides (IH, 116), the RhodospirUlum rubrum factor cannot be replaced by thiol reagents (117). 

Pseudomonas aeruginosa nitrite reductase of, 274, 275 transhydrogenase of, 53 molecular properties, 57 purification, 54, 56... 

San Pietro A, Kaplan NO, Colowick SP (1955) Pyridine nucleotide transhydrogenase VI. Mechanism and stereospecificity of the reaction in pseudomonas fluorescens. J Biol Chem 212 941-952 Schmidt J, Chen J, De Traglia M, Minkel D McFarland JT (1979) Solvent deuterium isotope effect on the liver alcohol dehydrogenase reaction. J Am Chem Soc 101 3634-3640 Schowen RL (1978) Catalytic power and transition-state stabilization. In Candour RD, Schowen RL (ed) Transition states of biological... 

Adenosine 5 -phosphate J nucleotide transhydrogenase from Pseudomonas aeruginosa ... 

Another mechanism for the interconversion of the pyridine nucleotides involves the enzyme pyridine nucleotide transhydrogenase, which has been purified from extracts of Pseudomonas jiuorescens. - It catalyzes a number of reactions, of which two are given below. (The reduced coenzymes are represented as TPNH and DPNH.)... 

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