The initial internal cyclization produces the monocyclic intermediate germacrene A; further cyclization and methyl transfer converts the intermediate into aristolochene. While in some species germacrene A remains as an enzyme-bound intermediate, it has been shown to be a minor product of the reaction in Penicillium roqueforti  (see also EC 126.96.36.199, germacrene-A synthase). The enzyme from Penicillium roqueforti requires Mg2+. Mn2+ can partially substitute, at low concentrations. Aristolochene is the likely parent compound for a number of sesquiterpenes produced by filamentous fungi.
EC 188.8.131.52 created 1992 as EC 184.108.40.206, transferred 1999 to EC 220.127.116.11, transferred 2000 to EC 18.104.22.168, modified 2006