α-Gurjunene synthase (EC 4.2.3.72) is an enzyme with systematic name (2E,6E)-farnesyl-diphosphate diphosphate-lyase ((–)-α-gurjunene-forming).^[1] This enzyme catalyses the following chemical reaction

(2E,6E)-farnesyl diphosphate ${\displaystyle \rightleftharpoons }$ (–)-α-gurjunene + diphosphate

Initial cyclization probably gives bicyclogermacrene in an enzyme-bound form.