Metabolism of Panthotenic Acid (B5)

1. PANTHOTHENIC ACID (B5]
Gandham. Rajeev
Department of Biochemistry,
Akash Institute of Medical Sciences
& Research Centre,
Devanahalli, Bangalore,
Karnataka, India.
E-Mail: gandhamrajeev33@gmail.com

3. PANTOTHENIC ACID (B5)

4.  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

5.  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

6.  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

7.  4-phosphopantetheine is converted to dephospho
coenzyme A by transfer of AMP
 Dephospho coenzyme A phosphorylated to form
CoA

8. OH - CH2 – C – CH – C – NH - CH2 - CH2 – 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

9. CH2 – C – CH – C – NH - CH2 - CH2 – CO-N-CH2 - CH2 - 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

10.  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
 Acyl groups are attached to SH groups of FAS

11.  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

12.  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

13.  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

14.  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

15.  Propionyl CoA is formed from oxidation of odd
chain fatty acids, isoleucine, methionine & valine
 Utilization:- Propionyl CoA is converted to
succinyl CoA

16. Acetyl CoA
Ketone Bodies
Pyruvate
Fatty Acids
Ketogenic amino acids
CO2 + H2O
Ketone Bodies
Fatty Acids
Acetyl Choline
Cholesterol

17.  Rich soueces: Yeast, eggs, liver & meat
 Good sources:- vegetables & grains
RDA:
Adults - 10 mg/day
Children - 7 mg/day

18.  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

20.  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