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FACTOR AFFECTING ENZYME -CATALYZED REACTION

PROBLEM BASED LEARNING (PBL)

PREPARED BY: MUHAMMAD ARIFF B. MAHDZUB

BACHELOR MEDICINE AND SURGERY (MBBS)

UNIVERSITY COLLEGE SHAHPUTRA, KUANTAN

FACTOR AFFECTING EMZYME -CATALYZED

REACTION

FACTOR AFFECTING ENZYME-

CATALYZED REACTION

CAN BE DIVIDED INTO TWO :

1. Due to frequency of collision

2. Due to energy barrier of reaction

FACTORS

FREQUENCY OF COLLISIONS

SUBSTRATE

CONCENTRATION

COENZYME CONCENTRATION

ENZYME CONCENTRATION

ENERGY BARRIER OF REACTION

TEMPERATURE

MODIFIER

pH

FREQUENCY OF

COLLISION:• Substrate concentration

substrate concentration,

the rate of reactions.

This is because more substrate molecules will be

colliding with enzyme molecules, so more products

will be formed

However, after a certain concentration, any

increase will have no effect on the rate of reaction

The enzymes will effectively become saturated, and

will be working at their maximum possible rate.

• Enzyme concentration

enzyme concentration,

rate of reactions

As more active site of enzyme presence to be

bind by substrate

as more enzymes will be colliding with substrate

molecules.

• Coenzyme concentration

• coenzymes are organic molecules that are

required by certain enzymes to carry out

catalysis.

• They bind to the active site of the enzyme

and participate in catalysis but are not considered

substrates of the reaction

• coenzymes often function as intermediate

carriers of electrons, specific atoms or functional

groups that are transfered in the overall reaction.

An example of this would be the role of NAD in the

transfer of electrons in certain coupled oxidation

reduction reaction

ENERGY BARRIER OF

REACTION

• Temperature

Increasing temperature, increases the Kinetic

Energy that molecules possess , will also

increases the possibility ES complex formed

As temperature increases, more bonds,

especially the weaker Hydrogen and Ionic bonds,

will break.

Breaking bonds within the enzyme will cause the

Active Site to change shape.

• pH

Enzymes in different locations have different

optimum pH values since their environmental

conditions may be different

Small changes in pH above or below the

Optimum do not cause a permanent change to

the enzyme, since the bonds can be reformed

However, extreme changes in pH can cause

enzymes to denature and permanently loose

their function

• MODIFIER

Can be either :

1. Positive modifier (activator)

2. Negative modifier (inhibitor)

The negative modifier can be

classified as :

1. Irreversible reaction

2. Reversible reaction

IRREVERSIBLE

INHIBITOR• Irreversible inhibitors usually

covalently modify an enzyme, and

inhibition therefore not be

reversed.

• They do not function by

destroying protein structure but

by specifically altering the active

site of their target.

• This inhibitor also often contain

reactive functional groups

REVERSIBLE INHIBITOR

Can be either:

1.Competitive

2.Noncompetitive

3.Uncompetitive

COMPETITIVE

INHIBITOR

• Will compete with substrate to

bind at active site of the enzyme

• Thus, the substrate can not bind

to form ES complex, but EI

complex were formed

• Can be overcome by increasing

the substrate concentration

NONCOMPETITIVE INHIBITOR

• No structural similarity to the

substrate

• Substrate and inhibitor will not

compete to bind to the active

site of enzyme

• Will bind to the allosteric site of

the enzyme

• Can not overcome by increasing

the substrate concentration

• binds equally well to the

enzyme whether or not it has

already bound the substrate

UNCOMPETITIVE INHIBITOR

• Uncompetitive inhibition, also

known as anti-competitive

inhibition

• Takes place when an enzyme

inhibitor binds only to the

complex formed between the

enzyme and the substrate (the E-

S complex).

• It will not bind to the free

enzyme

• The inhibition is not overcome by

high substrate concentration.