Subject: BIOCHEMISTRY
Presented to : Mam Samar Naz
Presented by: Group 6
VITAMIN B3(NIACIN)
VITAMIN 2 (RIBOFLAVIN)
VITAMIN H
VITAMIN B5 (PANTOTHENIC ACID)
Vitamin B3
• The other name of niacin are:
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Niacinamide
Nicotinic acid
Pellagra Preventing Factor
Nicotinamide riboside
Specially liver.
Limited amount of niacin can also be obtained from the metabolism of tryptophan
(60mg of tryptophan produce 1 mg of Niacin). (page 141) ( kynurenine pathway)
Metabolic Role
• Niacen produce two biologically active forms of coenzymes
• Nicotinaminde Adenine Dinucleotide (NAD)
• Nicotinamide Adenine dinucleotide phosphate (NADP).
• NAD and NADP help in redox (oxidation + reduction) reaction
• Reduced forms are NADH2 and NADPH2
• NAD and NADH2 act as coenzymes in the synthesis of ATPs through
oxidative phosphorylation.
• NADPH2 acts as a coenzyme and carries H+ ions. It uses its H+ ions
to keep the glutathione of RBCs in reduced form thus preventing
RBCs from oxidative damage.
Clinical use of Niacin
• It is used in the treatment of hyperlipidemias.
• It strongly inhibits lipolysis in adipose tissues (the primary producers of
circulating free fatty acids).
• Niacin causes decrease in liver triacylglycerol synthesis, which is required
for VLDL production.
• LDL (cholesterol rich lipoprotein) is derived from VLDL in the plasma.
• Thus both plasma triacylglycerol (in VLDL) and cholesterol (in VLDL and
LDL) are lowered.
Therefore Niacin is therapeutically used in the treatment of type –IIb
hyperlipoproteinemia (vaused VLDL and LDL)
CLINICAL NOTES NIACIN DEFICIENCY
• Deficiency of Niacin caused PELLAGRA
• Deficiency can be due to decreased oral intake or decrease tubular
reabsorption of tryptophan as seen in Hartnup disease.
• Pellagra is a disease involving the skin, gastrointestinal tract and
central nervous system.
• Symptoms: 3Ds i.e. Dermatitis, Diarrhea and Dementia and death if
not treated
Biotin
• Biotin is a coenzyme in carboxylation reactions, in which it serves as a
carrier of activated carbon dioxide (CO2).
• B vitamins, and specifically biotin, help keep your skin, hair, eyes,
liver, and nervous system healthy.
Sources
• Present in almost all foods particularly in liver, milk, and egg yolk.
Metabolic role
• Biotin is a coenzyme of carboxylase.
• It helps carboxylase in adding CO2 in certain chemical reaction.
Deficiency of biotin
• Deficiency seldom occurs, because the vitamins is widely distributed
in foods.
• Deficiency symptoms include dermatitis, glossitis, anorexia and
nausea.
Pantothenic acid (vitamin B5)
• Pantothenic acid provides (coenzyme-A) which helps in the transfer of
acyl groups.
• Examples of such compounds are succinyl Co-A, Fatty Acyl Co-A and
Acetyl Co-A
• It is also a component of fatty acid synthetase.
• Eggs, liver and yeast are the most important sources
• Its deficiency is not well characterized.