Pantothenic acid(B5)
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Transcript of Pantothenic acid(B5)
PANTHOTHENIC ACID (B5]
Gandham. Rajeev
Department of Biochemistry,Akash Institute of Medical Sciences & Research Centre,Devanahalli, Bangalore, Karnataka, India.
E-Mail: [email protected]
PANTOTHENIC ACID (B5)
Pantos means ‘everywhere’
It is widely distributed in nature
It is formerly known as chick anti-dermatitis
factor
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
METABOLISM
Coenzyme A & Form
Coenzyme A & 4-
phosphopantetheinePantothenic 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 - CH2 - CH2 – COO -
CH3
IOII
ICH3
OHI
Pantoic acid β - AlaninePantothenic 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 - CH2 - CH2 – CO-N-CH2 - CH2 - SH
CH3
IOII
ICH3
OHI
IOIPIOIP
O
-O - =O
-O - = O – CH2
H
N
NN
N
NH2
I
OH
HH H
-O - =O
OIPI
O-
Ribose - 3 P
Adenine
HI
Coenzyme A
Role of 4-phosphopantetheine4-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
Acyl groups are attached to SH groups of FAS
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
Biochemical functions
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
Role of acetyl CoA
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
Role of succinyl CoA
Propionyl CoA is formed from oxidation of
odd chain fatty acids, isoleucine,
methionine & valine
Utilization:- Propionyl CoA is converted to
succinyl CoA
Propionyl CoA
Acetyl CoA
Ketone Bodies
Pyruvate
Fatty Acids
Ketogenic amino acids
CO2 + H2OKetone BodiesFatty AcidsAcetyl Choline
Cholesterol
Rich soueces: Yeast, eggs, liver & meat
Good sources:- vegetables & grains
RDA:Adults - 10 mg/day
Children - 7 mg/day
Dietary sources
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
Deficiency
References
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