Enzyme-catalyzed redox

Niacin, which refers to nicotinic acid and nicotinamide, is the metabolic precursor to three nicotinamide coenzymes. These are essential for the activity of a large number of enzymes catalyzing redox reactions. Pellagra is a niacin deficiency disease. 

An enzyme-catalyzed redox reaction can be divided into two half-reactions, one producing electrons and the other consuming electrons. The standard apparent reduction potentials Fr° and E ° for the two half-reactions in an enzyme-catalyzed redox reaction at a specified pH and ionic strength determine E ° for the overall reaction, which is positive for a reaction that can occur spontaneously. A biochemical redox reaction at a specified pH can be represented schematically by... 

Enzymes catalyzing redox reactions in which oxygen serves as the electron acceptor may be divided in two groups those that catalyze substrate oxidation by electron transfer to the acceptor (oxidases and peroxidases) and those that catalyze substrate... 

It s often useful when thinking about enzyme-catalyzed redox reactions to recognize that a hydrogen atom is equivalent to a hydrogen ion, H, plus an electron, e . Thus, for the two hydrogen atoms removed in the oxidation of an alcohol, 2 H atoms = 2 + 2 e . When NAD is involved as the oxi-... 

Fireflies use flashes of light to attract mates. Light energy is released during an enzyme-catalyzed redox reaction. Luciferase is the name given to the enzyme that speeds up the reaction in which the organic molecule luciferin is oxidized. 

Walsh, C. 1978 Annu. Rev. Biochem. 47, 881-931 Chemical approaches to the study of enzymes catalyzing redox transformations. 

Oxidoreductases these enzymes catalyze redox reactions. Examples are oxidases that catalyze oxidation of a substrate by reducing molecular oxygen (02), and peroxidases that reduce H202. Laccases (EC 1.10.3.2) are oxidases that catalyze the oxidation of (poly)phenolic substrates. Reductases and dehydrogenases (EC 1.1.1) catalyze the reduction of carbonyls, using NADH/NADPH cofactors. Catalases (EC 1.11.1.6) catalyze the decomposition of H202 to 02 and H20. 

Transaminases are generally not considered to be enzymes catalyzing redox reactions, which is obvious considering the meaning of the E. C. code for transferases (E. C. 2.6.1.x = transferring amino groups). Nevertheless, the exchange of an amino functionality between an amino acid and an a-keto acid implies the oxidation of the amino acid. Transaminases are described elsewhere in this book (Chapter 12). 

NAD+/NADH or NADP+/NADPH also participate in a number of other enzyme-catalyzed redox reactions, which do not involve dehydrogenases in the classical sense as described earlier. These redox enzymes contain bound cofactors such as flavins, heme, and iron-sulfur clusters. One group of these enzymes is usually denoted diaphorase (DI) when used in analytical systems and includes both flavin-containing lipoamide and Kpoyl dehydrogenases (EC 1.8.1.4). 

Enzyme-Catalyzed Redox Reactions Accompanied by Capture of Proton by Acceptor in the Nonaqueous Phase... 

Hall, M. and Bommarius, A.S. (2011) Enantioenriched compounds via enzyme-catalyzed redox reactions. Chem. Reu., Ill, 4088-4110. 

The two pyridine nucleotide coenzymes, formerly known as coenzymes I and II, then for a period as DPN and TPN, and known nowadays as NAD and NADP (nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate), are involved in hundreds of enzyme-catalyzed redox reactions in vivo. Although a minority of these diverse reactions can use either of the two... 

Enzyme-catalyzed redox processes involve the transfer of two electrons in either one or two steps, each process requiring different coenzymes. Nicotinamide adenine dinucleotide (NAD) and its 2 -phosphate (NADP) coenzymes are involved in many two-electron... 

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