IUBMB Enzyme Nomenclature


Accepted name: lachrymatory-factor synthase

Reaction: (E)-alk-1-en-1-SO-peroxol = (Z)-alkanethial oxide

Glossary: alk-1-en-1-SO-peroxol = S-alk-1-en-1-ylthiohydroperoxide
alkanethial oxide = alkylidene-λ4-sulfanone = (alkylidenesulfaniumyl)oxidanide

Other name(s): LFS

Systematic name: (E)-alk-1-en-1-SO-peroxol isomerase [(Z)-alkanethial S-oxide-forming]

Comments: The enzyme is responsible for production of the irritating lachrymatory factor that is released by onions and related species when they are chopped. It acts of the product of EC, alliin lyase. The enzyme from Allium cepa (onion) acts on (E)-prop-1-en-1-SO-peroxol and produces (Z)-propanethial oxide, while the enzyme from Allium siculum (honey garlic) acts on (E)-but-1-en-1-SO-peroxol and produces (Z)-butanethial oxide.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Norris, P.G., Nunn, A.V., Hawk, J.L. and Cox, T.M. Genetic heterogeneity in erythropoietic protoporphyria: a study of the enzymatic defect in nine affected families. J. Invest. Dermatol. 95 (1990) 260-263. [PMID: 2384686]

2. Imai, S., Tsuge, N., Tomotake, M., Nagatome, Y., Sawada, H., Nagata, T. and Kumagai, H. Plant biochemistry: an onion enzyme that makes the eyes water. Nature 419 (2002) 685. [PMID: 12384686]

3. Eady, C.C., Kamoi, T., Kato, M., Porter, N.G., Davis, S., Shaw, M., Kamoi, A. and Imai, S. Silencing onion lachrymatory factor synthase causes a significant change in the sulfur secondary metabolite profile. Plant Physiol. 147 (2008) 2096-2106. [PMID: 18583530]

4. Kubec, R., Cody, R.B., Dane, A.J., Musah, R.A., Schraml, J., Vattekkatte, A. and Block, E. Applications of direct analysis in real time-mass spectrometry (DART-MS) in Allium chemistry. (Z)-butanethial S-oxide and 1-butenyl thiosulfinates and their S-(E)-1-butenylcysteine S-oxide precursor from Allium siculum. J. Agric. Food Chem. 58 (2010) 1121-1128. [PMID: 20047275]

[EC created 2021]

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