PANTHOTHENIC ACID (B5]

Gandham. Rajeev

Department of Biochemistry,Akash Institute of Medical Sciences & Research Centre,Devanahalli, Bangalore, Karnataka, India.

E-Mail: gandhamrajeev33@gmail.com

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