Bifunctional enzyme which is responsible for allene oxide biosynthesis via a two-step reaction; first the lipoxygenase reaction that converts polyunsaturated fatty acids such as arachidonate ((5Z,8Z,11Z,14Z)-eicosatetraenoate) into a (8R)-hydroperoxide intermediate ((8R)-hydroperoxy-(5Z,9E,11Z,14Z)-eicosatetraenoate) followed by the allene oxide synthase reaction that converts the hydroperoxide intermediate ((8R)-hydroperoxy-(5Z,9E,11Z,14Z)-eicosatetraenoate) into the allene oxide (8,9-epoxy-(5Z,9E,11Z,14Z)-eicosatetraenoate) (PubMed:9302294, PubMed:10559269). Shows preference for C20 or C22 highly polyunsaturated fatty acids and no activity with C18 fatty acids in vitro (PubMed:10559269). Fatty acid allene oxides are intermediates in the formation of cyclopentenones or hydrolytic products in marine systems, most notably the prostanoid-related clavulones (PubMed:29909837). (5Z,8Z,11Z,14Z)-eicosatetraenoate + O2 = (8R)-hydroperoxy-(5Z,9E,11Z,14Z)-eicosatetraenoate (8R)-hydroperoxy-(5Z,9E,11Z,14Z)-eicosatetraenoate = 8,9-epoxy-(5Z,9E,11Z,14Z)-eicosatetraenoate + H2O (5Z,8Z,11Z,14Z,17Z)-eicosapentaenoate + O2 = (8R)-hydroperoxy-(5Z,9E,11Z,14Z,17Z)-eicosapentaenoate (4Z,7Z,10Z,13Z,16Z,19Z)-docosahexaenoate + O2 = 10-hydroperoxy-(4Z,7Z,11E,13Z,16Z,19Z)-docosahexaenoate (8Z,11Z,14Z)-eicosatrienoate + O2 = (8R)-hydroperoxy-(9E,11Z,14Z)-eicosatrienoate (8Z,11Z,14Z)-eicosatrienoate + O2 = 10-hydroperoxy-(8Z,11Z,14Z)-eicosatrienoate (8Z,11Z,14Z)-eicosatrienoate + O2 = 11-hydroperoxy-(8Z,12E,14Z)-eicosatrienoate Binds 2 calcium ions per subunit. Binds 1 Fe cation per subunit. Binds 1 heme group per subunit. Lipoxygenase activity is stimulated by calcium, sodium, lithium and potassium ions. Calcium binding promotes interaction with membranes and thus facilitates access to substrates. Optimum pH is 7.0. Lipid metabolism; arachidonate metabolism. Lipid metabolism; fatty acid metabolism. Dimer. Calcium binding promotes binding to membranes. In the C-terminal section; belongs to the lipoxygenase family.