Nicotinamide adenine dinucleotide
Coenzyme
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other, nicotinamide.
From Wikipedia, under CC BY-SA. More on occurri.