Dehydrogenases cofactor

Glucose-6-phosphate dehydrogenase, cofactor regenerating system, 3 673... 

Dehydrogenase Dehydrogenase cofactor (reduced) cofactor (oxidised)... 

Pyruvate Dehydrogenase Cofactors and Mechanism Describe the role of each cofactor involved in the reaction catalyzed by the pyruvate dehydrogenase complex. 

Lactate dehydrogenase Cofactor (fructose-1,6-bi-sphosphate) requirement 70-fold activation without cofactor (fully active in the absence of cofactor) DNA shuffling + screening E. coli [208]... 

Bacillus stearothermophillus lactate dehydrogenase Cofactor (Fructose 1,6-bisphosphate) KMPyrUVate (mM)... 

P1 Methoxatin (1, cf. p 336) is a dehydrogenase cofactor in methylotrophic bacteria (also called... 

Methoxatin (cf p. 406) is a dehydrogenase cofactor in methylotrophic bacteria (also called PQQ PQQ = pyrroloquinoUne quinone). The synthesis of its triester J is achieved by the following sequence based on 2-methoxy-5-nitroaniline (X) ... 

Gofactors. Frequendy proteins exist in their native state in association with other nonprotein molecules or cofactors, which are cmcial to their function. These may be simple metal ions, such as Fe " in hemerythrin or Ca " in calmodulin a heme group, as for the globins nucleotides, as for dehydrogenases, etc. 

Hydroxyriboflavin. This compound [86120-61 -8] (26) was isolated as a green coen2yme of the NADH dehydrogenase from Peptostreptococms elsdenii and also from glycolate oxidase of porcine Hver. It is not fluorescent, and its stmcture was estabflshed by synthesis (106). The 5 -monophosphate serves as a cofactor for glycolate oxidase from pig Hver. 

Although the stmctures of ribavirin and selenazofutin are similar, they appear to exert their antiviral action at different enzyme sites along the same biochemical pathway. Selenazofutin forms the nicotinamide adenosiae dinucleotide (NAD) analogue, which inhibits IMP dehydrogenase by binding ia place of the NAD cofactor, and hence this potent reduction of guanylate pools is responsible for the antiviral effect of selenazofutin. 

A lot of analytical techniques have been proposed in recent decades and most of them are based on enzymes, called dehydrogenases, which are not sensitive to oxygen and need cofactors such as NAD". The key problems which seriously hamper a wide commercialization of biosensors and enzymatic kits based on NAD-dependent enzymes are necessity to add exogenous cofactor (NAD" ) into the samples to be analyzed to incorporate into the biologically active membrane of sensors covalently bounded NAD" to supply the analytical technique by NAD -regeneration systems. 

The conversion occurs through a multistep sequence of reactions catalyzed by a complex of enzymes and cofactors called the pyruvate dehydrogenase complex. The process occurs in three stages, each catalyzed by one of the enzymes in the complex, as outlined in Figure 29.11 on page 1152. Acetyl CoA, the ultimate product, then acts as fuel for the final stage of catabolism, the citric acid cycle. All the steps have laboratory analogies. 

Step 3 of Figure 29.12 Oxidation and Decarboxylation (2K,3S)-lsocitrate, a secondary alcohol, is oxidized by NAD+ in step 3 to give the ketone oxalosuccinate, which loses C02 to givea-ketoglutarate. Catalyzed by isocitrate dehydrogenase, the decarboxylation is a typical reaction of a /3-keto acid, just like that in the acetoacetic ester synthesis (Section 22.7). The enzyme requires a divalent cation as cofactor, presumably to polarize the ketone carbonyl group. 

Ethanol Electrodes The reliable sensing of ethanol is of great significance in various disciplines. The enzymatic reaction of ethanol with the cofactor nicotinamide-adenine dinucleotide (NAD+), in the presence of alcohol dehydrogenase (ADH)... 

Zinc, see also Enzyme cofactors as cofactor for alcohol dehydrogenase, 205 as cofactor for carbonic anhydrase, 197-200... 

Directed evolution of enzymes has been used to improve the reducing function of the enzymes. For example, this method was used to eliminate the cofactor requirement of B. stearothermophillus lactate dehydrogenase, which is activated in the presence of fructose 1,6-bisphosphate [12]. The activator is expensive and representative of the sort of cofactor complications that are undesirable in industrial processes. Three rounds of random mutagenesis and screening produced a mutant that is almost fully... 

The molyhdopterin cofactor, as found in different enzymes, may be present either as the nucleoside monophosphate or in the dinucleotide form. In some cases the molybdenum atom binds one single cofactor molecule, while in others, two pterin cofactors coordinate the metal. Molyhdopterin cytosine dinucleotide (MCD) is found in AORs from sulfate reducers, and molyhdopterin adenine dinucleotide and molyb-dopterin hypoxanthine dinucleotide were reported for other enzymes (205). The first structural evidence for binding of the dithiolene group of the pterin tricyclic system to molybdenum was shown for the AOR from Pyrococcus furiosus and D. gigas (199). In the latter, one molyb-dopterin cytosine dinucleotide (MCD) is used for molybdenum ligation. Two molecules of MGD are present in the formate dehydrogenase and nitrate reductase. 

In two sulfate-reducing bacteria we found oxygen-tolerant formate dehydrogenases with different subunit composition. The formate dehydrogenase from D. desulfuricans is an af3y protein whereas the one from D. gigas is an afi protein. Both proteins contain two MGD cofactors but the protein from D. desulfuricans contains four heme c attached to the y subunit (16 kDa). 

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