Involved in the biosynthesis of monoterpenes natural products (Ref.2). Monoterpene synthase that catalyzes mainly the formation of (E)-beta-ocimene and minor amounts of other monoterpenes (e.g. myrcene, (Z)-beta-ocimene, alpha- and gamma-terpinene) from geranyl diphosphate (GPP) (PubMed:20419468, Ref.2). (2E)-geranyl diphosphate = (E)-beta-ocimene + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Homodimer. Expressed in peltate glandular trichomes (PubMed:20419468). Present in flowers, leaves and stems (Ref.3). The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family.