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Allosteric Site vs. Active Site — What's the Difference?

By Tayyaba Rehman — Published on November 16, 2023
The active site is where substrates bind and reactions occur in an enzyme, while the allosteric site is a separate site where molecules bind to regulate enzyme activity. The former directly facilitates reactions; the latter influences them indirectly.
Allosteric Site vs. Active Site — What's the Difference?

Difference Between Allosteric Site and Active Site


Key Differences

Nature and Role: The active site of an enzyme is the region where the substrate molecules bind and undergo a chemical reaction. The allosteric site, in contrast, is a distinct location on the enzyme where regulatory molecules, called allosteric modulators, bind.
Functional Mechanism: While the active site is directly responsible for catalytic reactions, the allosteric site plays a regulatory role. When an allosteric modulator binds to the allosteric site, it can either activate or inhibit the enzyme's activity at the active site.
Binding Specificity: Substrates bind to the active site due to its complementary shape and chemistry, ensuring specificity. On the other hand, the allosteric site binds modulators that may not resemble the substrate, but their binding can alter the enzyme's conformation.
Regulation and Feedback: The active site doesn't usually change its function unless acted upon by external factors. However, the allosteric site allows for feedback mechanisms, where end products can inhibit or enhance enzyme activity, ensuring metabolic control.
Impact on Enzyme Shape: Binding at the active site typically doesn't change the enzyme's overall shape. In contrast, binding at the allosteric site often induces conformational changes, affecting the enzyme's overall activity.

Comparison Chart

Nature and Role

Regulatory site of the enzyme
Reaction site of the enzyme

Functional Mechanism

Influences enzyme activity indirectly
Directly facilitates enzymatic reactions

Binding Specificity

Binds modulators distinct from substrates
Binds specific substrates due to complementary shape


Allows for feedback mechanisms
Directly participates in catalysis

Impact on Shape

Induces conformational changes in the enzyme
Doesn't typically induce major conformational changes

Compare with Definitions

Allosteric Site

Where regulatory molecules bind to influence enzyme function.
An inhibitor at the allosteric site can deactivate the enzyme.

Active Site

The central hub of enzymatic catalysis.
The reaction was facilitated at the active site.

Allosteric Site

Can either enhance or inhibit enzymatic activity.
Activation at the allosteric site boosted the reaction rate.

Active Site

Dictates the enzyme's catalytic properties and reaction specificity.
The unique properties of the active site define the enzyme's function.

Allosteric Site

Involved in feedback regulation of enzyme activity.
End products binding to the allosteric site provide metabolic control.

Active Site

The region on an enzyme where substrates bind and reactions occur.
The substrate fits perfectly into the active site of the enzyme.

Allosteric Site

Induces conformational changes when bound with modulators.
Upon binding, the allosteric site changed the enzyme's shape.

Active Site

Ensures specificity due to its complementary shape to substrates.
Only the correct substrate can bind to the enzyme's active site.

Allosteric Site

A distinct location on an enzyme away from the active site.
The molecule bound to the allosteric site, altering enzyme activity.

Active Site

May be influenced by factors like pH and temperature.
The active site became deformed at high temperatures.

Common Curiosities

How do inhibitors affect the active site?

Inhibitors can block or change the active site, preventing substrate binding.

What primary function does an active site serve?

The active site is where substrates bind and enzymatic reactions occur.

Why is the active site's shape crucial?

The shape ensures specificity, allowing only the correct substrate to bind.

How does the allosteric site differ from the active site?

The allosteric site is a regulatory region, while the active site is where reactions take place.

Can a molecule bind simultaneously to both sites?

While uncommon, certain molecules can interact with both the active and allosteric sites.

Are all allosteric sites inhibitory?

No, allosteric sites can be either inhibitory or activating.

Does every enzyme have both an active and an allosteric site?

Not all enzymes have allosteric sites, but all have active sites.

Why are allosteric sites essential for metabolic pathways?

They allow for feedback regulation, maintaining metabolic balance.

How do allosteric inhibitors function?

They bind to the allosteric site, inducing a conformation that decreases enzyme activity.

Can environmental factors affect the active site?

Yes, factors like pH and temperature can impact the active site's shape and function.

Do allosteric sites exist on proteins other than enzymes?

Yes, some non-enzymatic proteins can have allosteric sites influencing their function.

How do allosteric activators work?

They bind to the allosteric site, promoting a conformation that enhances enzyme activity.

Can an enzyme have multiple active sites?

Yes, some multi-subunit enzymes can have several active sites.

Can mutations affect the active site?

Yes, mutations can alter the active site, potentially affecting enzyme function.

How do enzymes achieve specificity?

The unique shape and chemistry of the active site ensure specificity to certain substrates.

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Author Spotlight

Written by
Tayyaba Rehman
Tayyaba Rehman is a distinguished writer, currently serving as a primary contributor to As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.

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