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PANTHOTHENIC ACID (B5]
Gandham. Rajeev
Department of Biochemistry,
Akash Institute of Medical Sciences
& Research Centre,
Devanahalli, Bangalore,
Karnataka, India.
E-Mail: [email protected]
Pantos means ‘everywhere’
It is widely distributed in nature
Its metabolic role as a coenzyme A (Discovered by
Lipmann)
Chemistry:
Pantothenic acid is composed of pantoic acid
joined to β – alanine by a peptide bond
It is stable to heat & destroyed by acid & alkali
Absorption: It is present in food either free form
or coenzyme form
Coenzyme form is hydrolyzed to free form by
intestinal pyrophosphatase
Free pantothenic acid is absorbed from upper part
of small intestine by sodium dependent transport
system
Transport it enters portal circulation & transported
to various tissues
Coenzyme A & Form
Coenzyme A & 4-phosphopantetheine
Pantothenic acid is first phosphorylated to form 4-
phospho pantothenic acid
4-phosphopantothenic acid is converted into 4-
phosphopantothenylcysteine by the transfer of
cysteine molecule to 4-phosphopantothenic acid
4-phosphopantothenylcysteine is decarboxylated
to form 4-phosphopantetheine
4-phosphopantetheine is converted to dephospho
coenzyme A by transfer of AMP
Dephospho coenzyme A phosphorylated to form
CoA
OH - CH2– C – CH – C – NH - CH
2- CH
2– COO
-
CH3
I
O
II
I
CH3
OH
I
Pantoic acid β - Alanine
Pantothenic acid
4-phospho pantothenate
4-phosphopantothenyl cysteine
Cysteine
ATP
ADP
ATP
ADP
4-phosphopantotheine
Dephospho-coenzyme A
Coenzyme A
ATP
PPi
CH2– C – CH – C – NH - CH
2- CH
2– CO-N-CH
2- CH
2- SH
CH3
I
O
II
I
CH3
OH
I
I
O
I
P
I
O
I
P
O
-O - =O
-O - = O – CH2
H
N
NN
N
NH2
I
OH
HH H
-O - =O
O
I
P
I
O-
Ribose - 3 P
Adenine
H
I
Coenzyme A
Role of 4-phosphopantetheine
4-phosphopantetheine is required for De novo
synthesis of FA
4-phosphopantetheine is a carrier of acyl groups
4-phosphopantetheine is attached to ACP of FAS
complex
4-phosphopantetheine contributes to peripheral
SH group of FAS complex
The functions of pantothenic acid are exerted
through coenzyme A or CoA (A for acetylation)
Co A is involved in all the metabolisms
It plays a role in integrating various metabolic
pathways
Coenzyme A has a terminal thiol or sulfhydryl
group (-SH)
SH group is the reactive site
Hence CoA-SH is used
Acyl groups are linked to coenzyme A by thioester
bond, to give acyl CoA
CoA serves as a carrier of activated acetyl or acyl
groups
Enzymes requiring Coenzyme A as
cofactor:
Pyruvate dehydrogenase complex
α- Ketoglutarate dehydrogenase complex
FAS complex
Thiolase, HMG CoA synthase
Acetyl Co A is formed from oxidation of pyruvate
to, amino acids, FA, ketone bodies
Utilization: Acetyl CoA is utilized for oxidation
through TCA cycle to provide energy
It essential for formation of Acetylcholine
Acetylcholine is neurotransmitter
Acetyl CoA is the substrate for synthesis of FA,
cholesterol, Amino acids, & ketone bodies
Succinyl Co A is formed from propionyl CoA and
α- ketoglutarate
Propionyl CoA is formed from oxidation of odd
chain FA,valine, isoleucine, methionine
Utilization succinyl CoA is oxidized through TCA
cycle
Succinate is utilized for metabolism ketone
bodies
It is also used for synthesis of heme
Propionyl CoA is formed from oxidation of odd
chain fatty acids, isoleucine, methionine & valine
Utilization:- Propionyl CoA is converted to
succinyl CoA
Rich soueces: Yeast, eggs, liver & meat
Good sources:- vegetables & grains
RDA:
Adults - 10 mg/day
Children - 7 mg/day
Deficiency of pantothenic acid (CoA) is rare in
humans
Experimental studies:
By giving antagonist of B5 such as ω - methyl
pantathenic acid
Burning feet syndrome is observed
It is characterized by numbness & tingling of toes,
burning pain in the feet, sleep disturbances,
dermatitis & depression
Harper’s Biochemistry 25th Edition.
Fundamentals of Clinical Chemistry by Tietz.
Text Book of Medical Biochemistry-A R Aroor.
Text Book of Biochemistry-DM Vasudevan
Text Book of Biochemistry-MN Chatterjea
Text Book of Biochemistry-Dr.U.Satyanarana