under the supervision of

Dr.YASSER AZIMASSISTANT PROFESSOR

DEPT.OF APPLIED CHEMISTRY,AMUYaseer.azim@gmail.com

ABU DARDAAbudarda.ms@amu.ac.inTEAMLEADER ZHCET-AMU

Myoglobin

Oxygen transport by Hb

Hemoglobin

Oxygen binding site

Co- opretivity Effect

Bohr Effect

Royal Mirage

Heme Protein

Heme protein

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ABOUT HEME1. Fe2+ + Protoporphyrin IX = HEME

2. Mb and Hb are “heme” proteins.

3. Bound to the protein permanently, either covalently or noncovalently bound or both.

4. Porphyrins are colored.

– Iron porphyrin gives red color to blood.

– Magnesium porphyrin gives green color

to plants.

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STRUCTURE OF HEMEPROTIEN

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SYNTHESIS OF HEME

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DEGRADATION OF HEME

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BIOLOGICAL FUNCTIONS OF HEMEPROTIEN

• Oxygen transport & store –Mb,Hb

• Catalysis- peroxidases, cytochrome c oxidase

• Electron transfer- cytochrome a, cytochrome

b, cytochrome c.

• Defense- catalase.

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DISORDERS

• Porphyria

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hemoglobinROYAL MIRAGE

• Hemoglobin is the basic metalloprotein that is present in

the red blood cells which are responsible for carrying

oxygen.

• Hb + 4O2 HbO8

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→

→

FUNCTION OF RBC

The main function of red blood cells-

Transfer of O2 from lungs to tissues.

Transfer of CO2 from tissues to lungs.

Each red blood cells has 640 million molecules

of Hb

Haemoglobin protien constituting 1/3 of the red blood

cells.

Molar mass of Hb-64500

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SYNTHESIS OF HEMOGLOBIN(Hb)Two Parts

HaemGlobin

HEAMo PROSTHETIC GROUP

o CONTAINING Fe+2 ION

GLOBINo HEME CONTAINING PROTEINS

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Hemoglobin is found exclusively in RBCs.

Its main function is to transport oxygen from lungs to the tissues

& carbon dioxide & hydrogen protons from tissues to lungs.

LUNGS TISSUES

Function of hemoglobin

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O2

CO2

→→

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Tetramer complex

Contain four globin molecules

Each globin contains 1 heme

Fe+2 ion in centre of heme

Fe+2 is known as feroheme

Anaemia symptoms

Loss of energy

Leg cramps

Difficulty concentrating

Rapid heart beat

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o Seafood

o Eggs

o Dried fruits

o Fruits

o Chocolate

o Meat

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OXYGEN TRANSPORT BY HAEMOGLOBIN

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Complex Protein containing HAEM (Iron)

1 molecule of Haem combines with 4 molecules of

Oxygen to form OXYHAEMOGLOBIN

Hb + 4O 2 → HbO8

Haemoglobin Oxygen Oxyhaemoglobin

The reaction is Reversible

→

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At lungs there is low (carbon dioxide) so Hb has a

greater affinity for Oxygen- so picks up more

Oxyhaemoglobin releases its oxygen where it is most

needed :to the actively respiring tissues

At the Tissues there is high (carbon dioxide) this reduces

Hb affinity for oxygen so it gives it up

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Oxygen dissociation curve of Oxyhaemoglobin

The curve shows that:

at relatively low oxygen concentrations there is uncombined haemoglobin in the blood and little or no oxyhaemoglobin, e.g. in body tissue

at relatively high oxygen concentrations there is little or no uncombinedhaemoglobin in the blood; it is in the form of oxyhaemoglobin, e.g. in the lungs

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1. Deoxygenated blood is transferred from heart to lungs

2. CO2 in blood is exchanged for O2 in lungs

3. The oxygenated blood is then carried by Haemoglobin from lungs to heart

4. Heart pumps out the oxygenated blood to arteries towards tissues

5. This Oxygen in blood is exchanged for CO2 in tissues

6. The deoxygenated blood is finally transferred to heart

The Circulatory system

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myoglobin

History facts

• First protein to have its three-dimensional structure

• In 1958, John Kendrew and associates successfully

determined the structure of myoglobin by high-

resolution X-ray crystallography.

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WHAT IS MYOGLOBIN?

• Myoglobin is an iron- and oxygen-binding protein

found in the muscle tissue of vertebrates in general

and in almost all mammals.

• Molecular weight-16,700 Daltons.

• Number of residues- 153

• Number of Polypeptide Chains-1

• Myoglobin forms pigments responsible for making

meat red.

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Structure & functions:

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• Myoglobin (Mb) is a single-chain globular protein

of 153 or 154 amino acids.

• Containing a heme (iron-containing porphyrin)

prosthetic group in the center.

• It has eight alpha helices and a hydrophobic core.ROYAL MIRAGE

Functions:• Stores oxygen in muscles.

• During starving condition it release oxygen to the

body tissues.

• Myoglobin forms pigments responsible for making

meat red.

• High concentrations of myoglobin in muscle cells

allow organisms to hold their breaths longer.

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Role in disease:

• Rhabdomyolysis

• Acute renal failure

• It is a sensitive marker for muscle injury.

• it is a potential marker for heart attack in patients

with chest pain.

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OXYGEN BINDING SITE

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WHAT IS OXYGEN BINDING?

• Binding of Oxygen ( O2) to Heme proteins i.e., haemoglobin, myoglobin & hemocyanin etc.

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HAEMOGLOBIN & MYOGLOBIN• Haemoglobin & myoglobin are oxygen transporter and

storage proteins.

• Haemoglobin is tetrameric while Myoglobin is

monomeric.

• Hb: two α chains of 141 residues & two β chains of 146

residues.

• Hb: Molecular weight- 64,000 daltons.

• Mb: 153 amino acids, Molecular weight-17,700 daltons.

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• Fe in the heme group is the site for oxygen binding.

• Hb forms a reversible bond with the Oxygen.

• When Oxygen binds Ferrous state ( Fe+2) changes to Ferric state (Fe +3).

• Single Hb unit can bind 4 Oxygen molecule.

• Binding of Oxygen with Hb is called cooperative binding.

HOW OXYGEN BINDS WITH HEMOGLOBIN?

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• Its binding is similar to hemoglobin.

• Fe in Mb is in ferrous state- that binds oxygen.

• Oxidation of Fe yields 3+ charge i.e., ferric state-

metmyoglobin does not bind oxygen.

• One Mb unit can bind only one Oxygen molecule.

• Its binding is called non-cooperative binding.

BINDING OF OXYGEN WITH MYOGLOBIN

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• Hb undergoes a conformational changes on binding

Oxygen.

• Two major conformation of Hb-

R (relaxed) and T( tense) state.

• T- state is more stable (deoxyhemoglobin).

• Binding O2 to hemoglobin subunit in T-state triggers

a change in conformation to R-state.

CONFORMATIONAL CHANGES IN Hb

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• Heme group is non-planar in deoxygenated state.

• Oxygen binding pulls the Fe into the heme plane.

• Fe pulls its His F8 ligand along with it.

• In oxygenated state, heme group is planar.

• The F helix moves when oxygen binds.

• Total movement of Fe is 0.029 nm-0.29 Å.

GEOMETRICAL CHANGES

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Cooperativity of Haemoglobin

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What is cooperativity effect?

The phenomenon where the addition of oxygen to one Hemegroup facilites its addition to the other Heme groups of Haemoglobin is known as Cooperativity Effect

The cooperativity of O2 binding to Haemoglobin influences how much of the blood O2 is delivered to any particular tissue

This property is called an OXYGEN DISSOCIATION CURVE

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Shows the amount of O2 that is

bound to Haemoglobin (Y-axis)

as a function of partial pressure

of O2 in the blood plasma (X-

axis)

Because of the cooperativity

this dissociation curve is

S-shaped.

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• Successive oxygenation reactions of haemoglobin are as follows:

Hb + O2 𝑯𝒃𝒐𝟐Hbo2 + O2 Hb(O2)2

Hb(O2)2 Hb(02)3

Hb(O2)3 + O2 Hb(O2)4

Overall rate constant

K = [𝑯𝒃 𝑶

𝟐 𝟒]

𝑯𝒃 𝟎𝟐𝒏 ; K = Binding constant & n = Hill constant

Value n=4 represents MAXIMUM COOPERATIVITY EFFECT

Binding constant of oxyhaemoglobin

K1

K2

K3

K4

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→→→

→→→→→

Explanation of Cooperativity Effect

In deoxyhaemoglobin,the heme group is out of the plane and

iron is in +2 oxidation state and in high spin

Oxygen binds to the heme group through vacant sixth

coordination site and iron is in +3 oxidation state and in

low spin

These changes in the heme unit due to its coordination with

O2 trigger the cooperativity phenomenon

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Bohr effect

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About Christian Bohr

Christian Harald Lauritz Peter Emil Bohr

• 1880 MS from University of Leipzig

•1886 Prof. university

of Copenhagen

•1891 Dead space

•1903 Bohr effect

•Danish physiologist

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•The effect of pH and CO2

concentration on the binding and

release of oxygen by hemoglobin

•Lowering the pH

•Raising the partial pressure of co2

•The release of O2 from oxyhemoglobin

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BOHR EFFECT

Frac

tio

nal

sat

ura

tio

n

Oxygen partial pressure

At lower pH, His 146 is protonated which favours

the deoxyHBconformation thereby

leading to release of O2

Carbamate ROYAL MIRAGE

O2O2

O2O2O2

O2O2

O2

Raising partial pressure of carbon dioxide

Lowering pH

Oxyhemoglobin Deoxyhemoglobin

Peripheral tissues

O2

2H+ + 2HCO3- 2H2CO3

2CO2 + 2H2O

Carbonic anhydrase

2CO2 + 2H2O

Exhaled

Carbonic anhydrase

2HCO3- + 2H+

4O2

Lungs

2H2CO3

Hb + 4O2

Hb + 2H+

(buffer)

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