Page 213 - Biochemistry PharmD General

3. Niacin (nicotinic acid)

• The biologically active co-enzyme forms are
nicotinamide adenine dinucleotide (NAD+) and its

phosphorylated derivative, nicotinamide adenine
dinucleotide phosphate (NADP+).

• NAD+ and NADP+ serve as co-enzymes in oxidation-
reduction reactions in which they undergo reduction
to NADH and NADPH, respectively. N.B. NAD+ is
used mainly for oxidative catabolism while NADPH is
used mainly for reductive biosynthesis. NADPH is also
a co-enzyme for cytochrome P450 reductase
responsible for drug metabolism.

• Deficiency of niacin causes pellagra, a disease

involving the skin, GIT and CNS. The symptoms of

pellagra are dermatitis, diarrhea and dementia(3 Ds);

if untreated, death occurs. 212