Monoterpene synthase (mono-TPS) involved in the biosynthesis of monoterpene natural products (PubMed:16415217). Catalyzes the conversion of (2E)-geranyl diphosphate (GPP) into (-)-limonene (PubMed:16415217). Not able to use geranylgeranyl pyrophosphate (GGPP) and farnesyl pyrophosphate (FPP) as substrates (PubMed:16415217). (2E)-geranyl diphosphate = (4S)-limonene + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Terpene metabolism; oleoresin biosynthesis. Monomer. Accumulates in apical leaders upon wounding in resistant but not in susceptible to white pine weevil (Pissodes strobi) plants. 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. Tpsb subfamily.