Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide (NAD) is a cofactor central to metabolism. In metabolism, NAD is involved in redox reactions, carrying electrons from one reaction to another. Because of the importance of these functions, the enzymes involved in NAD metabolism are targets for drug discovery.
About Nicotinamide adenine dinucleotide in brief
Nicotinamide adenine dinucleotide (NAD) is a cofactor central to metabolism. In metabolism, NAD is involved in redox reactions, carrying electrons from one reaction to another. The cofactor is, therefore, found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction forms NADH, which can then be used as a reducing agent to donate electrons. It is also used in other cellular processes, most notably as a substrate of enzymes in adding or removingchemical groups to or from, respectively, proteins. Because of the importance of these functions, the enzymes involved in NAD metabolism are targets for drug discovery. NAD+ and NADH strongly absorb ultraviolet light because of the adenin and nicotinamide in them. Both forms of this coenzyme are white amorphous powders that are hygroscopic and highly water-soluble. The solids are stable if stored dry and in the dark. Upon decomposition, they form colorless, colorless solutions of NAD+ or NADH that are enzyme inhibitors. For example, NAD+ absorbs at higher wavelengths, with a second peak in UV absorption at 339 nm, with an extinction coefficient of 6,220 nm. This makes it simple to measure the simple conversion of one enzyme to another in simple assays of the coenzymes of NAD+. This makes the conversion of NAD to NADH a simple measure of the conversion to another enzyme in simpler assays.
The reaction is easily reversible, when NADH reduces another molecule and is re-oxidized to NAD+. This means the coen enzyme can continuously cycle between the NAD+ & NADH forms without being consumed. The NAD+ chemical species’ superscripted addition sign reflects the formal charge on one of its nitrogen atoms. It’s actually a singly charged anion — carrying a ionic charge of 1 — under conditions of physiological pH. NADH is a doubly charge anion, because of its two bridging phosphate groups. It can be synthesized from simple building-blocks from either tryptophan or aspartic acid, each a case of an amino acid. More complex components are taken up from nutritive compounds such as niacin; similar compounds are produced by reactions that break down the structure of NAD, providing a salvage pathway that “recycles” them back into their respective active form. The nucleosides each contain a ribose ring, one withadenine attached to the first carbon atom and the other with nicotinamide at this position. The nicotinamonide moiety can be attached in two orientations to this anomeric carbon atom. The compound exists as two diastereomers, It is the β-nicotinamide diastsereomer of NAD+, that is found in organisms. The nucleotides are joined together by a bridge of two phosphate groups through the 5′ carbons.