Factor Affecting Enzyme

7/28/2019 Factor Affecting Enzyme

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Factors

affectingenzyme

Substrate

concentration

Enzyme

concentration

Temperature

pH value

Chemical

denaturation



Concentration of

substrate is limiting

As the enzyme concentration increases, the rate of reaction will increase.

However, equilibrium will be reached when no matter how much enzyme is

present, the reaction will not occur any quicker.

Enzyme concentration



Substrate concentration

Increasing [S]

increases collision

rate and increases

reaction rate

All active sites are

occupied. Enzymes are

working at maximum rate.

Increasing the substrate concentration will increase the rate of reaction

until it reaches a maximum. After this point, increases in substrate

concentration will not increase the rate of reaction.





At low temperature, the rate is very low.

Increasing temperature, the rate of

enzyme activity increases.

At optimum temperature, rate of

reaction is the highest.

After optimum temperature, rate of

reaction decreases..





pH changes

•Extreme of pH will denature protein.

•Even small changes around neutral pH can affect the

ionisation of amino acid side-chains in the active site.

•A change in one pH unit Is a ten fold change in H+ ion

concentration.



•Pepsin – acidic condition in stomach

•Amylase – approximately neutral

•Trypsin – alkaline condition in the small intestine



Chemical denaturation

• Isolated enzyme can be denatured by changes in

chemical conditions.

• Examples:

1. high salt concentration disrupt ionic interaction

between different regions of the chain.

2. urea denatures protein by disrupting the H2

bond.

• Certain chemical inhibitors totally inactivate enzyme and

their effects are irreversible.



What happen? Terrorist attack on the Tokyo

underground by using sarin gas

When? March 1995

How does it happen? • Sarin gas is poisonous.•It is similar n struture with DFP (di-(1-

methylethyl)fluorophosphate)

•DFP is a reagent which bind to serine

residues in enzyme. It function as nerve

gas.



Enzyme needs assistant-

Prosthetic groups and coenzyme

• Many enzymes require a non-protein group,

cofactor to function as catalyst.

• If not, there is no enzyme activity.



• organic groups that are permanently

bound to the enzyme

Prostheticgroup

• cations - positively charged metal ions

• temporarily bind to the active site of theenzyme.

Activators

• vitamins or made from vitamins

• not permanently bound to the enzyme

molecule, but combine with the enzyme-

substrate complex temporarily

Coenzyme

Type of cofactor



• Water and ion channels in cell

membranes are form by

protein.

• These protein has enzyme-like

function.

• They are trans-membrane

protein (a protein that goes

from one side of a membrane

through to the other side of

the membrane)



Example……..

• sodium-potassium pump in

neurones.

• pump ejects 3 sodium ions for

every 2 potassium ions that itpulls in.

• inside of the cell builds up a

net negative charge

compared with the

surrounding "extracellular"

fluid.

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Factor Affecting Enzyme