Monoterpene synthase involved in the biosynthesis of volatile compounds present in floral scent (PubMed:25056927). Mediates the conversion of (2E)-geranyl diphosphate (GPP) into sabinene and sub-products such as alpha-thujene, alpha-pinene, beta-pinene, myrcene, alpha-phellandrene, alpha-terpinene, beta-phellandrene, gamma-terpinene and terpinolene (PubMed:25056927). Unable to use farnesyl diphosphate (FPP) as substrate (PubMed:25056927). (2E)-geranyl diphosphate = diphosphate + sabinene (2E)-geranyl diphosphate = diphosphate + terpinolene (2E)-geranyl diphosphate = alpha-pinene + diphosphate (2E)-geranyl diphosphate = beta-pinene + diphosphate (2E)-geranyl diphosphate = beta-myrcene + diphosphate (2E)-geranyl diphosphate = alpha-terpinene + diphosphate (2E)-geranyl diphosphate = beta-phellandrene + diphosphate (2E)-geranyl diphosphate = diphosphate + gamma-terpinene Binds 3 Mg(2+) or Mn(2+) ions per subunit. kcat is 0.057 sec(-1) with (2E)-geranyl diphosphate as substrate. Optimum pH is 7.5 (PubMed:25056927). Active at pH between 6.0 and 9.0 (PubMed:25056927). Optimum temperature is 30 degrees Celsius. Secondary metabolite biosynthesis; terpenoid biosynthesis. Highly expressed in flowers, petals and sepals, but almost undetectable in vegetative organs. During flower development, first observed in petals after about 40 hours, with a sharp increase between 32 and 48 hours, and a decrease during flower senescence. 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.