Nicotinamide adenine dinucleotide binding site

Nishino, T., and Nishino, T., 1987, Evidence for a tyrosine residue in the nicotinamide adenine dinucleotide binding site of chicken liver xanthine dehydrogenase. Biochemistry 26 3068n3072. 

Figure 3.1 Amino add side-chain groups involved in binding NAD at the active site of an enzyme. The enzyme is glyceraldehyde dehydrogenase. More than 20 amino acids, the position of which in the primary structure is indicated by the number, counting from the N-terminal amino acid, are involved in the binding. This emphasises the complexity of the binding that is responsible for the specificity of the enzyme for NAD (depicted in bold). The molecular structure of nicotinamide adenine dinucleotide (NAD ) provided in Appendix 3.3.

Triazine (e.g., atrazine, simazine) and substituted urea (e.g., diuron, monuron) herbicides bind to the plastoquinone (PQ)-binding site on the D1 protein in the PS II reaction center of the photosynthetic electron transport chain. This blocks the transfer of electrons from the electron donor, QA, to the mobile electron carrier, QB. The resultant inhibition of electron transport has two major consequences (i) a shortage of reduced nicotinamide adenine dinucleotide phosphate (NADP+), which is required for C02 fixation and (ii) the formation of oxygen radicals (H202, OH, etc.), which cause photooxidation of important molecules in the chloroplast (e.g., chlorophylls, unsaturated lipids, etc.). The latter is the major herbicidal consequence of the inhibition of photosynthetic electron transport. 

Some proteins contain other native fluorophores in addition to fluorescent amino acids. These include cofactors such as nicotinamide adenine dinucleotide (fluorescent in its reduced, NADH state) and flavin adenine dinucleotide (FAD). NADH is weakly fluorescent in water, but its fluorescence yield increases markedly on binding to a protein-binding site with an emission peak around 470 nm (3). FAD and flavin mononucleotide (FMN) are also fluorescent with an emission maximum around 520 nm, but fluorescence is quenched on binding to many flavoproteins (4). 

Abbreviations FASN, fatty acid synthase ACC, acetyl-CoA-carboxylase ACL, ATP-citrate lyase NADPH, nicotinamide adenine dinucleotide phosphate MAT, malonyl acetyl transferases KS, ketoacyl synthase KR, p-ketoacyl reductase DH, p-hydroxyacyl dehydratase ER, enoyl reductase TE, thioesterase ACP, acyl carrier protein VLCFA, very long chain fatty acids ELOVL, elongation of very long chain fatty acids SCDl, stearoyl-CoA desaturase-1 AMPK, AMP-activated kinase ME, malic enzyme FASKOL, liver-specific deletion of FAS PPARa, Peroxisome Proliferator-Activating Receptor alpha HMG-CoA, 3-hydroxy-3-methyl-glutaryl-CoA SREBP, sterol response element binding protein SIP, site-one protease S2P, site-two... 

Catalysis by flavoenzymes has been reviewed and various analogues of FAD have been prepared e.g. P -adenosine-P -riboflavin triphosphate and flavin-nicotinamide dinucleotide ) which show little enzymic activity. The kinetic constants of the interaction between nicotinamide-4-methyl-5-acetylimidazole dinucleotide (39) and lactic dehydrogenase suggest the presence of an anionic group near the adenine residue at the coenzyme binding site of the enzyme. ... 

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