ABSTRACT
Oxidation-reduction (redox) reactions are of extreme importance for all organisms from bacteria to mammals, regulating cellular processes and providing cells with energy and building blocks. In order to maintain various cellular functions, redox statuses in a cell are kept balanced by a set of mechanisms, in which pyridine nucleotides and thiol redox buer systems are the key players. Pyridine nucleotides, reduced and oxidized forms of both nicotinamide adenine dinucleotide (NADH/NAD+) and its phosphate (NADPH/NADP+), are essential in the redox reactions of various metabolites. NAD+ receives electrons to form NADH during the oxidation of various nutrients, such as sugars and fats; NADH is then oxidized by the electron transfer chain associated with adenosine triphosphate (ATP) production (see Chapter 1). NADPH provides the reducing equivalents for biosynthetic reactions of anabolic pathways and antioxidant defense in the control of cellular oxidative stress. Finally, appropriate redox state of proteins is maintained by thiols via the redox buer system comprised of glutathione and thioredoxin (Trx). Glutathione is the most abundant free thiol in cells and the major player in redox homeostasis and function of cellular proteins through interaction with redox proteins (e.g., Trx, glutaredoxin, peroxiredoxin, and protein disulde isomerase). It also serves as the reducing substrate for antioxidant enzymes,
8.1 Introduction ......................................................................................179 8.2 Genetically Encoded Fluorescent Sensors ....................................181 8.3 Genetically Encoded Fluorescent Sensors for NADH ................182
