Alliinase

Alliinases are a class of enzymes found in plants of the genus Allium, such as garlic and onions. Alliinase is responsible for catalyzing chemical reactions that produce the volatile chemicals that give these foods their flavors, odors, and tear-inducing properties. Alliinases are part of the plant's defense against herbivores. Alliinase is normally sequestered within a plant cell, but when the plant is damaged by a feeding animal, the alliinase is released to catalyze the production of the pungent chemicals. This tends to have a deterrent effect on the animal. The same reaction occurs when onion or garlic is cut with a knife in the kitchen.

In garlic, an alliinase enzyme acts on the chemical alliin converting it into allicin.

Reaction scheme for the conversion: cysteine → alliin → allicin

In onions, the enzyme acts on sulfenic acids to produce syn-propanethial-S-oxide.

References

• Genuine Garlic:Alliinase from Allium sativum.