Sesquiterpene synthase involved in the biosynthesis of beta-caryophyllene as the major product and trace amounts of alpha-humulene. Produces exclusively the (-)-(E)-beta caryophyllene enantiomer. (2E,6E)-farnesyl diphosphate = (-)-(E)-beta-caryophyllene + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. High expression in disk florets, moderate expression in ray florets and detected in leaves and stems, but not in roots. 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. Tpsa subfamily.