Desamido NAD

The vitamin niacin (nicotinic acid) is converted to NAD through the intermediate, desamido NAD. 

An AMP moiety is transferred from ATP to nicotinate ribonucleotide to form desamido-NAD. The final step is the transfer of the ammonia generated from the amide group of glutamine to the nicotinate carboxyl group to form NAD+. 

As in other reactions in which either ammonia or the amide group of glutamine is utilized (amination of UTP to form CTP, synthesis of NAD from desamido-NAD, and of guanylate from xanthylate), the carbamyl phosphate synthetase II reaction is inhibited by the glutamine analogues, azaserine and diazo-oxo-norleucine (see Chapter 5). 

In the human, nicotinic acid reacts with 5-phosphoribosyl-I-pyrophosphate to form nicotinic acid mononucleotide, which then reacts with ATP to produce desamido-NADIthc intermediate dinucleotide with the nicotinic acid moiety). Finally, the latter intermediate is converted to NAD (originally called coenzyme I) by transformation of the emboxyl of the nicotinic acid moiety to the amide by glutamine. Thb final step is catalyzed by NAD synthetase NADP is produced from NAD by ATT under kinase catalysis. ... 

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