NAD vs NADP
In all organisms, there is a certain universal set of molecules that carry out versatile functional in cellular metabolic pathways and in regulatory processes. ATP is the most important molecule which acts as the universal energy currency of the cell. Apart from that, NAD and NADP molecules are well known cofactors involved in cellular metabolism, and they serve vital roles in metabolic conversion as signal transducers. NAD and NADP are pyridine nucleotides that contain two nucleotides, adenine base, and necotinamide. Basically protein is involved in the biosynthesis of NAD and NADP.
NAD (Nicotinamide Adenine Dinucleotide)
All living cells have NAD as a coenzyme. It is made of two nucleotides joined through their phosphate groups. An adenine group is bound to one nucleotide while, the other nucleotide contains necotinamide. There are two known NAD biosynthetic routes. In the denovo biosynthesis route, NAD+ is synthesized from aspertate and dihydroxyacetone phosphate or from tryptophan. The salvage pathways utilize degradation products, namely nicotinic acid and nicotinamide to produce NAD+. The functions of NAD in metabolism are acting as a donor of ADP ribose moieties in ADP ribosylation, as a coenzyme in redox reactions, as a precursor of the second messenger molecule cyclic ADP-ribose, and as a substrate for bacterial DNA ligases.
NADP (Nicotinamide Adenine Dinucleotide Phosphate)
The reduction form of NADP is NADPH. It is synthesized via the phosphorylation of NAD by NADK (NAD Kinase). In animals, it is a vital molecule to the cellular oxidative defense system and for reductive synthesis. NADP molecules play an important role in maintaining a pool of reducing equivalents that is essential to counteract oxidative damage and for other detoxifying reactions (NADPH system can produce free radicals in immune cells, and these free radicals are used to destroy pathogens in the body). It is also used for metabolic pathways such as lipid and cholesterol synthesis, and fatty acid elongation in animal cells.
In plants and other photosynthetic organisms, NADPH is produced in the last step of electron chain of the light reaction of photosynthesis by ferredoxin-NADP+ reductase enzyme. This NADPH is then used as reducing power in the Calvin cycle to assimilate carbon dioxide.
What is the difference between NAD and NADP?
• NADP is the phosphorylated form of NAD.
• NADP has an additional phosphate group while that additional phosphate group is absent in NAD molecule.
• NAD is produced either in a ‘de novo’ pathway from amino acids or in salvage pathways by recycling nicotinamide back to NAD. In contrast, NADP biosynthesis requires phosophorylation of NAD catalyzed by NAD kinase.