Brief Communication | Published:

Plant biochemistry

An onion enzyme that makes the eyes water


A flavoursome, user-friendly bulb would give no cause for tears when chopped up.


The irritating lachrymatory factor that is released by onions when they are chopped up has been presumed to be produced spontaneously following the action of the enzyme alliinase, which operates in the biochemical pathway that produces the compounds responsible for the onion's characteristic flavour1,2,3,4. Here we show that this factor is not formed as a by-product of this reaction, but that it is specifically synthesized by a previously undiscovered enzyme, lachrymatory-factor synthase. It may be possible to develop a non-lachrymatory onion that still retains its characteristic flavour and high nutritional value by downregulating the activity of this synthase enzyme.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Brodnitz, M. H. & Pascale, J. V. J. Agric. Food Chem. 19, 269–272 (1971).

  2. 2

    Block, E., Penn, R. E. & Revelle, L. K. J. Am. Chem. Soc. 101, 2200–2201 (1979).

  3. 3

    Shen, C. & Parkin, K. L. J. Agric. Food Chem. 48, 6254–6260 (2000).

  4. 4

    Block, E. Angew. Chem. Int. Ed. Engl. 31, 1135–1178 (1992).

  5. 5

    Adamu, I., Joseph, P. K. & Augusti, K. T. Experientia 38, 899–901 (1982).

  6. 6

    Ariga, T., Oshiba, S. & Tamada, T. Lancet 1, 150–151 (1981).

  7. 7

    Makheja, A. N. & Bailey, J. M. Agents Actions 29, 360–363 (1990).

Download references

Author information

Competing interests

The authors declare no competing financial interests.

Correspondence to S. Imai.

Rights and permissions

To obtain permission to re-use content from this article visit RightsLink.

About this article

Further reading

Figure 1: Obligatory involvement of the enzyme lachrymatory-factor synthase in the production of lachrymatory factor (LF) in onion.
Figure 2


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.