Binds 3 Mg(2+) ions per subunit. Up-regulated by methyl jasmonate. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Site-directed mutagenesis and 3-D homology modeling suggest that the structure of the N-terminal domain is important in facilitating proper folding of the protein to form a catalytically active enzyme. Belongs to the terpene synthase family.