PANTHOTHENIC ACID (B5]

Gandham. Rajeev

Department of Biochemistry,

Akash Institute of Medical Sciences

& Research Centre,

Devanahalli, Bangalore,

Karnataka, India.

E-Mail: gandhamrajeev33@gmail.com

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