Involved in monoterpene (C10) olefins biosynthesis. (2E)-geranyl diphosphate = (4S)-limonene + diphosphate Binds 3 Mg(2+) ions per subunit. Optimum pH is 6.5. Optimum temperature is 40 degrees Celsius. Terpene metabolism; (4S)-limonene biosynthesis; (4S)-limonene from geranyl diphosphate: step 1/1. Trichome. 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.