Non-functional sesquiterpene synthase having less than 1% of the activity found in cv. Delprim. Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Monomer. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). The allele found in cv. B73 encodes an inactive enzyme while the two alleles found in cv. Delprim encode an active (TPS5A) and an inactive (TPS5B) enzyme (PubMed:15075399). Belongs to the terpene synthase family.