Monoterpene biosynthesis in the liverwort Conocephalum conicum:: Demonstration of sabinene synthase and bornyl diphosphate synthase

(-)-Sabinene is the major monoterpene produced by a European strain of the liverwort Conocephalum conicum. A cell-free extract from in vitro cultured plants catalysed the cyclization of geranyl diphosphate to sabinene. The responsible monoterpene cyclase was partially purified and characterized as an operationally soluble enzyme of M-r 65 000, with a pH optimum at 7.5 and a requirement for a divalent metal ion as the only cofactor, with Mg2+ preferred. The general properties of the sabinene synthase from C. conicum resemble those of other monoterpene cyclases from gymnosperms and angiosperms. A North American strain of the liverwort produces (+)-bornyl acetate as the major monoterpene and it was demonstrated that bornane-type monoterpenes are derived from geranyl diphosphate in this liverwort, as in higher plants, by the action of bornyl diphosphate synthase. (C) 1997 Elsevier Science Ltd. All rights reserved.