Single enzymatic reactions oxidation

The bacterial enzyme chorismate mutase-prephenate dehydrogenase is peculiar because it is a single protein unit with two catalytic activities. It catalyzes the sequential reactions of mutation of chorismate to prephenate and then the reaction that leads to the formation of phenylalanine and tyrosine, through oxidation of prephenate. The first of these reactions is interesting because it is one of the few strictly single-substrate enzymatic reactions it entails... 

We already mentioned that the enzymes involved in the P-oxidation of fatty acids are located in the mitochondria. The source of two-carbon fragments for the biosynthesis of both fatty acids and isoprenoids like cholesterol is acetyl CoA, which is generated by oxidative metabolism in the mitochondria. Acetyl CoA cannot escape from the mitochondria, but it can be exported to the cyosol as citrate, where it is reconverted to oxaloacete and acetyl CoA. Fatty acid (and cholesterol) biosynthesis takes place in the cyosol, and requires bicarbonate, which is incorporated into acetyl CoA to form malonyl CoA by acetyl CoA carboxylase. The biosynthesis of fatty acids, mostly the Cie palmitate (Chapter 4), requires one molecule of acetyl CoA and seven molecules of malonyl CoA. In animals, the seven enzymatic reactions which are required for fatty acid synthesis are present in a single multifunctional protein complex, known as fatty acid synthase. The synthase also contains an acyl-carrier protein... 

In this section, we present the data on the enzymatic reactions of explosives relevant to the general cytotoxicity mechanisms of nitroaromatics (1) their single-electron enzymatic reduction to radicals accompanied by the formation of the reactive oxygen species (oxidative stress type of cytotoxicity) and (2) their two-electron reduction to nitroso and hydroxylamino metabolites causing the cytotoxicity by their covalent binding to proteins and DNA. 

Laccases (benzenediohoxygen oxidoreductases, EC 1.10.3.2) are a diverse group of multi-copper enzymes, which catalyze oxidation of a variety of aromatic compounds. Laccases oxidize their substrates by a one-electron transfer mechanism. They use molecular oxygen as the electron acceptor. The substrate loses a single electron and usually forms a firee radical. The unstable radical may undergo further laccase-catalysed oxidation or non-enzymatic reactions including hydration, disproportionation, and polymerisation. ... 

Continuous enzymatic production of xylitol with simultaneous coenzyme regeneration in a charged membrane reactor was studied (210). An NADH dependent xylose reductase from C. tenuis catalyzed the reduction of xylose. This was coupled to enzymatic oxidation of glucose by glucose dehydrogenase from Bacillus cereus to make achievable an up to 10,000-fold regeneration of NADH per cycle of discontinuous conversion. Under suitoble conditions, 300 g/L of substrate could be converted in yields above 96% in one single batch reaction. 

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