Alliinase: The Enzyme Responsible for Garlic's Signature Smell and Health Benefits

December 8, 2025 •

3 min read

An intact, raw clove of garlic has very little odor until it is crushed or chopped. This is because the potent compounds that give garlic its signature aroma and many of its health benefits are only released through the action of a specific enzyme: alliinase.

Quick Summary

The enzyme alliinase is activated when garlic is damaged, converting the precursor compound alliin into the highly reactive allicin. This process is responsible for garlic's pungent odor and is a key to unlocking its therapeutic properties.

Key Points

Alliinase is the Key: The enzyme that gives garlic its characteristic odor and potent benefits is alliinase (alliin lyase).
Activation Required: Alliinase is activated only when raw garlic is physically damaged, such as by crushing or chopping.
A Cascade of Compounds: Alliinase acts on the precursor alliin to form allicin, which quickly breaks down into many other organosulfur compounds.
Timing is Everything: To maximize allicin content, crush garlic and let it rest for 10-15 minutes before cooking.
Heat Deactivates: High heat inactivates the alliinase enzyme, preventing allicin from forming, though other compounds may persist.
Beyond Allicin: While allicin is a key compound, its breakdown products and other garlic compounds contribute to its overall health effects.

What is Alliinase?

Alliinase, also known as alliin lyase, is a pyridoxal 5-phosphate-dependent enzyme naturally present in garlic (Allium sativum). It is a homodimeric glycoprotein that exists within specialized microcompartments, or vacuoles, within the garlic clove's cells. This physical separation from its primary substrate is the reason an undamaged clove of garlic is relatively odorless.

The Chemical Reaction: From Alliin to Allicin

When garlic is physically damaged—through crushing, chopping, mincing, or chewing—the cellular compartments rupture, allowing alliinase to come into contact with the odorless sulfur-containing compound, alliin, which is stored in the cytoplasm. This initiates a rapid and powerful enzymatic reaction that produces the unstable intermediate, sulfenic acid. Two molecules of sulfenic acid then condense spontaneously to form allicin (diallyl thiosulfinate), the compound primarily responsible for garlic's pungent aroma and a wide range of biological activities.

Maximizing Allicin Production

To maximize the health-promoting effects of this enzymatic reaction, simple preparation techniques are key. Here is the process:

Crush or chop the garlic finely to ensure widespread cellular disruption and maximum contact between alliinase and alliin.
Allow to rest for 10 to 15 minutes after crushing but before heating. This "stand time" allows the alliinase enzyme to complete its work and produce the maximum amount of allicin before it can be inactivated by heat.
Avoid prolonged high heat. The alliinase enzyme is heat-sensitive and will be inactivated by cooking, which stops the production of allicin.

The Fate of Allicin: Breakdown into Other Compounds

Allicin is highly reactive and unstable, with a half-life of less than three days at room temperature. Once formed, it quickly breaks down into a variety of other beneficial organosulfur compounds. These derivatives, such as diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), are also responsible for many of garlic's therapeutic properties and can persist longer than allicin itself. Different preparation methods, such as aging garlic in alcohol and water to create Aged Garlic Extract (AGE), produce a different profile of sulfur compounds like S-allylcysteine (SAC), which are more stable and water-soluble.

Alliinase vs. Heat and Acid: A Comparison


Feature	Raw/Crushed Garlic	Heated/Cooked Garlic
Alliinase Activity	Active and highly effective.	Inactivated, especially with prolonged, high heat.
Allicin Production	Rapid and high production within seconds.	Minimal to no production due to enzyme deactivation.
Predominant Compounds	Alliin is converted primarily to allicin, which then yields other volatile organosulfur compounds.	Alliin is not converted by the inactivated enzyme. Other sulfur compounds might form or degrade.
Therapeutic Profile	Potent antimicrobial, antioxidant, and immunomodulatory effects linked to high allicin and volatile compound levels.	Lower levels of allicin and its immediate breakdown products; focus shifts to more stable compounds and broader health benefits.

Conclusion

Understanding the role of alliinase is central to appreciating and harnessing garlic's full potential. The enzyme acts as a biological trigger, converting an inert compound into a cascade of potent sulfur-rich molecules when the clove is damaged. From its antimicrobial effects to its cardiovascular benefits, the distinctive properties of garlic are intricately linked to the activity of this crucial enzyme. By employing simple techniques like crushing and resting, you can ensure that this enzymatic process is maximized, unlocking a burst of flavor and a wealth of health-promoting compounds with every clove. The science is clear: how you prepare your garlic directly influences its potency. You can learn more about garlic's health effects from authoritative sources like the Oregon State University's Linus Pauling Institute.

Frequently Asked Questions

The primary enzyme in garlic is alliinase, also known as alliin lyase. It is responsible for triggering the chemical reaction that creates allicin, the compound known for garlic's pungent aroma and health properties.

You activate alliinase by physically damaging the garlic clove, such as by crushing, chopping, mincing, or chewing. This action breaks the cell walls, allowing the enzyme to interact with its substrate, alliin.

If you don't crush the garlic, the alliinase enzyme and its substrate alliin will remain separated in different cellular compartments. The heat from cooking will then inactivate the enzyme before the compounds can mix and form allicin, resulting in less potent flavor and fewer therapeutic benefits.

Cooking, especially with high heat, inactivates the alliinase enzyme and reduces the formation of allicin and its unstable derivatives. However, some other beneficial compounds remain, so the health benefits are diminished but not completely eliminated.

Yes. Alliin is a stable, odorless compound found in intact garlic cells. Allicin is a highly reactive compound produced when the alliinase enzyme acts on alliin after the clove is crushed.

To maximize the health benefits, crush or chop the garlic and let it rest for 10 to 15 minutes before adding it to your cooking. This allows the alliinase reaction to complete before the heat deactivates the enzyme.

No. While allicin and its derivatives (such as ajoenes and diallyl polysulfides) are widely studied for their benefits, garlic also contains other health-promoting compounds, including water-soluble substances like S-allylcysteine (SAC) found in aged garlic extract.