Discovery of overlooked enzyme in onion and its application

Article abstract of DOI:10.1080/10426507.2019.1603704

When onions (Allium cepa) are chopped, cells are broken, propanthial S-oxide (lachrymatory factor; LF) is released and it makes our eyes water. LF had long been believed to be formed non-enzymatically from 1-propenesulfenic acid (PSA), a putative reaction product of alliinase acting on trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide (1-PRENCSO). During the course of our study for the discoloration of Allium plants, however, we got a clue that some unknown enzyme responsible for the LF formation should be present in the crude onion alliinase preparation. In this study, we report the discovery of this new enzyme called lachrymatory factor synthase (LFS), and its application such as non-lachrymatory onions.