Co-enzyme Forms of Niacin and NAD+ Reduction

What is the primary function of NADPH in cellular reactions?

What is the outcome of niacin deficiency?

What is the underlying cause of dermatitis in pellagra?

Which enzyme is involved in the synthesis of NAD+ from tryptophan?

What is the characteristic skin lesion seen in pellagra?

Which of the following is NOT a symptom of pellagra?

What is the role of NAD+ in the cell?

What is the name of the pathway that generates NADPH?

What is the resulting compound when niacin is attached to a ribose phosphate?

What is the difference between NAD+ and NADP+?

What happens to the nitrogen atom of niacinamide in the oxidized form of the co-enzyme?

What is the net result of NAD+ accepting one H atom and one e?

Which of the following enzymes is NOT a NAD+ dependent enzyme?

What is the result of the oxidation of NADH in the respiratory chain?

What is the function of NAD+ in the process of reduction?

What is the difference between the oxidized and reduced forms of the co-enzyme?

Co-enzyme Forms of Niacin

Niacin is converted to its co-enzyme forms, Nicotinamide adenine dinucleotide (NAD+) and Nicotinamide adenine dinucleotide phosphate (NADP+).
Niacin is attached to a ribose phosphate to form a mononucleotide, then attached to AMP to form the dinucleotide.
The nitrogen atom of niacinamide contains one positive charge, hence the structure is abbreviated as NAD+.
NADP+ has one more phosphoric acid attached to the ribose of the AMP.

Reduction of NAD+

In the oxidized form, the nitrogen of the nicotinamide residue has a positive charge.
In the process of reduction, NAD+ accepts one hydrogen atom fully and one electron, and the positive sign in the molecule is removed.
NAD+ dependent enzymes include lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, and more.

NADH and NADPH

One NADH molecule is oxidized in the respiratory chain to generate 2½ ATPs.
NADPH is used almost exclusively for reductive biosynthetic reactions.
NADPH generating reactions include glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase.
NADPH utilizing enzymes include glutathione reductase and more.

Niacin Deficiency

Deficiency of niacin leads to the clinical condition called pellagra.
Pellagra is caused by the deficiency of Tryptophan as well as Niacin.
Symptoms of pellagra include dermatitis, diarrhea, and dementia.

Pellagra Symptoms

Dermatitis: bright red erythema occurs, especially in the feet, ankles, and face.
Diarrhea: may be mild or severe with blood and mucus, leading to weight loss.
Dementia: frequently seen in chronic cases, with delerium, irritability, and more.

Learn about the conversion of niacin into its co-enzyme forms, NAD+ and NADP+, and the reduction of NAD+. Understand the structure and formation of these molecules.