What are Oxidoreductases?

Oxidoreductases are a class of enzymes that catalyze oxidoreduction reactions (17).  Oxidoreductases catalyze the transfer of electrons from one molecule (the oxidant) to another molecule (the reductant).  Oxidoreductases catalyze reactions similar to the following, A + B → A + B where A is the oxidant and B is the reductant (19).  Oxidorecuctases can be oxidases or dehydrogenases.  Oxidases are enzymes involved when molecular oxygen acts as an acceptor of hydrogen or electrons.  Whereas, dehydrogenases are enzymes that oxidize a substrate by transferring hydrogen to an acceptor that is either NAD+/NADP+ or a flavin enzyme.  Other oxidoreductases include peroxidases, hydroxylases, oxygenases, and reductases. Peroxidases are localized in peroxisomes, and catalyzes the reduction of hydrogen peroxide. Hydroxylases add hydroxyl groups to its substrates. Oxygenases incorporate oxygen from molecular oxygen into organic substrates. Reductases catalyze reductions, in most cases reductases can act like an oxidases (17).

Oxidoreductase enzymes play an important role in both aerobic and anaerobic metabolism.  They can be found in glycolysis, TCA cycle, oxidative phosphorylation, and in amino acid metabolism.  In glycolysis, the enzyme glyceraldehydes-3-phosphate dehydrogenase catalyzes the reduction of NAD+ to NADH.  In order to maintain the re-dox state of the cell, this NADH must be re-oxidized to NAD+, which occurs in the oxidative phosphorylation pathway.  Additional NADH molecules are generated in the TCA cycle.  The product of glycolysis, pyruvate enters the TCA cycle in the form of acetyl-CoA.  During anaerobic glycolysis, the oxidation of NADH occurs through the reduction of pyruvate to lactate.  The lactate is then oxidized to pyruvate in muscle and liver cells, and the pyruvate is further oxidized in the TCA cycle.  All twenty of the amino acids, except leucine and lysine, can be degraded to TCA cycle intermediates.  This allows the carbon skeletons of the amino acids to be converted into oxaloacetate and subsequently into pyruvate.  The gluconeogenic pathway can then utilize the pyruvate formed (20)

This website will focus on isocitrate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, and glutammate dehydrogenase.

Overview of Aerobic Metabolism

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