In enzymology, an allene-oxide cyclase () is an enzyme that belongs to the family of isomerases, specifically a class of other intramolecular oxidoreductases. The systematic name of this enzyme class is (9Z)-(13S)-12,13-epoxyoctadeca-9,11,15-trienoate isomerase (cyclizing).
The allene oxide of linolenic acid (i.e., (9Z)-(13S)-12,13-epoxyoctadeca-9,11,15-trienoate) is converted by allene oxide cyclase to jasmonic acid ((15Z)-12-oxophyto-10,15-dienoate).
As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes , , , , , and .