| MadSci Network: Botany |
The irritant formed in cut onions is syn-propanethial-S-oxide. A recent study from Japan (Imai et al. 2002) indicates that a previously unknown onion enzyme is responsible for the formation of syn-propanethial-S-oxide. The enzyme is lachrymatory-factor synthase. Previously, syn-propanethial-S-oxide was thought to spontaneously form from propenylsulfenic acid. Inactivating lachrymatory- factor synthase via genetic engineering could result in tear-free onion cultivars. Syn-propanethial-S-oxide is a fairly small molecule. The structure is CH3- CH=CH-S-O References Why does chopping an onion make you cry? Synthesis of syn-propanethial-S-oxide Why do my eyes tear when I peel an onion? Imai, S., N. Tsuge, M. Tomotake, Y. Nagatome, H. Sawada, T. Nagata, and H. Kumagaiet. 2002. Plant biochemistry: an onion enzyme that makes the eyes water. Nature, v. 419: 685 (Oct. 17).
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