ABZYMESABZYMES

SHIJINA.A SHIJINA.A

BCH 10-05- 04BCH 10-05- 04

S2 MSc BIOCHEMISTRYS2 MSc BIOCHEMISTRY

IntroductionIntroduction Antibodies and enzymes share the ability to bind Antibodies and enzymes share the ability to bind

with compounds with great specificity and high with compounds with great specificity and high affinity.affinity.

This property has been exploited in the development This property has been exploited in the development of antibodies with catalytic activity.of antibodies with catalytic activity.

Antibodies have been 1Antibodies have been 1stst characterized as proteins characterized as proteins produced by the IS for binding with molecules called produced by the IS for binding with molecules called antigens.antigens.

One basic difference between antibodies and One basic difference between antibodies and enzymes is that the former binds the complementary enzymes is that the former binds the complementary structure in its ground state , while enzymes bind in structure in its ground state , while enzymes bind in high energy state high energy state

In 1986 , the 1In 1986 , the 1stst monoclonal catalytic antibodies monoclonal catalytic antibodies termed termed abzymesabzymes against a chemically stable analog against a chemically stable analog of the transition state of a reaction were obtainedof the transition state of a reaction were obtained

Abzymes are catalytic antibodies having structural Abzymes are catalytic antibodies having structural complementarity for the transition state of an complementarity for the transition state of an enzyme catalyzed reaction.enzyme catalyzed reaction.

They bind strongly to the transition state with high They bind strongly to the transition state with high association constant, enhancing the reaction rate .association constant, enhancing the reaction rate .

Abzymes reduce rotational entropy .Abzymes reduce rotational entropy .

Sources of AbzymesSources of Abzymes

Abzymes are usually artificial constructs.Abzymes are usually artificial constructs. They also obtained from human and animal serum.They also obtained from human and animal serum. Found in normal humans and ii patients with Found in normal humans and ii patients with

autoimmune diseases.autoimmune diseases. These are capable of hydrolyzing proteins, DNA, These are capable of hydrolyzing proteins, DNA,

RNA, polysaccharides etc RNA, polysaccharides etc

Protabzymes and DNA AbzymesProtabzymes and DNA Abzymes

Natural abzymes with proteolytic activity are called Natural abzymes with proteolytic activity are called Protabzymes .e.g.: hydrolysis of specific proteins in Protabzymes .e.g.: hydrolysis of specific proteins in patients with autoimmune diseases such as patients with autoimmune diseases such as bronchial Asthma ,multiple sclerosis. bronchial Asthma ,multiple sclerosis.

DNA hydrolyzing activity are called DNA abzymes.DNA hydrolyzing activity are called DNA abzymes. The pathogenic role of DNA abzymes is not quite The pathogenic role of DNA abzymes is not quite

clear. However they act as a powerful regulator of clear. However they act as a powerful regulator of apoptosis. apoptosis.

Production of abzymesProduction of abzymes

Antibody molecules are produced by the immune Antibody molecules are produced by the immune system to bind and neutralize foreign substances system to bind and neutralize foreign substances called antigens called antigens

Foreign proteins of bacteria , viruses and some Foreign proteins of bacteria , viruses and some chemical molecules called haptens , act as chemical molecules called haptens , act as antigens .antigens .

Transition state analogs are molecules which are Transition state analogs are molecules which are more stable than the transition state itself , but they more stable than the transition state itself , but they mimic its 3D structure .mimic its 3D structure .

If injected into the blood stream of an animal , If injected into the blood stream of an animal , transition state analogs act as haptens and elicit transition state analogs act as haptens and elicit antibody production.antibody production.

Abs are isolated from the serum of the animal and Abs are isolated from the serum of the animal and used as abzymes .used as abzymes .

Theoretically ,if the Ab binds to a transition state Theoretically ,if the Ab binds to a transition state molecule, it may be expected to catalyze a molecule, it may be expected to catalyze a corresponding chemical reaction by forcing corresponding chemical reaction by forcing substrates into transition state geometry.substrates into transition state geometry.

Transition state

Transition state analog(act as Ag)

Substrate

Ab complementary to transition state

PdtPdtmicemice

Examples for abzymesExamples for abzymes

1.1. Hydrolysis of hydroxy ester by abzymesHydrolysis of hydroxy ester by abzymes

Hydroxy ester forms a cyclic intermediate Hydroxy ester forms a cyclic intermediate during hydrolysis.during hydrolysis.

Cyclic phosphonate ester is the structural analog Cyclic phosphonate ester is the structural analog of the cyclic intermediate.of the cyclic intermediate.

This analog is used as an antigen to elicit This analog is used as an antigen to elicit antibodies.antibodies.

These antibodies bind the cyclic intermediate , These antibodies bind the cyclic intermediate , increasing the reaction rate .increasing the reaction rate .

Hydroxy ester Cyclic intermediate Hydroxy ester Cyclic intermediate δδ--lactone phenol lactone phenol

Anti –cyclic intermediate antibody Anti –cyclic intermediate antibody (Abzymes)(Abzymes)

Cyclic phosphonate ester Cyclic phosphonate ester (antigen) ,mimic cyclic intermediate(antigen) ,mimic cyclic intermediate

2.2. Hydrolysis of ester by abzymesHydrolysis of ester by abzymes• Ester forms a tetrahedral intermediate during Ester forms a tetrahedral intermediate during

hydrolysishydrolysis• The phosphate analog of ester mimic this intermediate, The phosphate analog of ester mimic this intermediate,

used as antigen to elicit antibodies.used as antigen to elicit antibodies.• These antibodies recognize and bind to tetrahedral These antibodies recognize and bind to tetrahedral

intermediate and stabilize it resulting in rate intermediate and stabilize it resulting in rate accelerationacceleration. .

Biosynthesis of HemeBiosynthesis of Heme• It involves introduction of Fe2+It involves introduction of Fe2+ into into

protophorphyrine by ferrochelatase.protophorphyrine by ferrochelatase.• This process is called metallation This process is called metallation • Metallation involves the distortation of pyrole ring Metallation involves the distortation of pyrole ring

by 36by 36ºto create a bent transition stateºto create a bent transition state

• This state is apt for the entry Fe2+This state is apt for the entry Fe2+• Methyl mesoporphyrin , an analog of the bent Methyl mesoporphyrin , an analog of the bent

transition state , is used as antigen to elicit transition state , is used as antigen to elicit abzymes. abzymes.

• These abzymes bind the bent transition state and These abzymes bind the bent transition state and distorts the porphyrin facilitating metallation rate distorts the porphyrin facilitating metallation rate 2500fold higher 2500fold higher

Reactions catalyzed by AbzymesReactions catalyzed by Abzymes

1.1. Amide hydrolysis Amide hydrolysis

2.2. Trans- EsterificationTrans- Esterification

3.3. photo cleavagephoto cleavage

4.4. PhotodimerizationPhotodimerization

5.5. Decarboxylation Decarboxylation

6.6. OxidationOxidation

7.7. CyclizationCyclization

8.8. Reduction of diketone Reduction of diketone

9.9. Hydrolysis of enol ethers Hydrolysis of enol ethers

Applications Applications

Synthesis of simple organic molecules Synthesis of simple organic molecules Drug developmentDrug development Treat CancerTreat Cancer Treat allergyTreat allergy treat viral and bacterial infectiontreat viral and bacterial infection

Reference Reference

Enzymology –T. DevasenaEnzymology –T. Devasena

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