Final answer:
Niacin, or Vitamin B3, is converted to NAD+ and NADP+, which act as coenzymes involved in the oxidation and reduction of metabolic processes, contributing to energy production and synthesis of fatty acids and cholesterol.
Step-by-step explanation:
Mechanism of Action for Niacin/Nicotinic Acid
The mechanism of action (MOA) for niacin, also known as nicotinic acid or Vitamin B3, primarily involves its conversion to nicotinamide (also called niacinamide), which then combines with a ribose phosphate. This compound is further esterified to an adenine nucleotide to form nicotinamide adenine dinucleotide (NAD+). Both NAD+ and its phosphate form, NADP+, act as coenzymes for oxido-reductases, working as electron acceptors during enzymatic removal of hydrogen atoms. NAD+ is particularly important as a coenzyme for dehydrogenases in the oxidation of various foodstuffs, while NADPH serves as a coenzyme for reductases in the synthesis of fatty acids and cholesterol.
The chemical structure of niacin includes a pyridine ring with a carboxylic acid group. The importance of NAD+ and NADP+ in metabolic processes, such as the Krebs cycle and the electron transport chain, is well established since they play a critical role in energy production within the cell.
Niacin also has a role in the metabolism of certain aromatic compounds like benzene, as well as halogenated compounds, through a process involving the amino acid cysteine.