Proton Transfer in a Reaction Catalyzed by Onion Lachrymatory Factor Synthase

Abstract

We produced a single deuterated lachrymatory factor (propanthial S-oxide, m/z=91) in a model reaction system comprising purified alliinase, lachrymatory factor synthase (LFS), and (E)-(+)-S-(1-propenyl)-L-cysteine sulfoxide ((E)-PRENCSO) in D₂O. Onion LFS reacted with the degraded products of (E)-PRENCSO by alliinase, but not with those of (Z)-PRENCSO. These findings indicate that onion LFS is an (E)-1-propenylsulfenic acid isomerase.