PURIFICATION AND CHARACTERIZATION OF S-LINALOOL SYNTHASE, AN ENZYME INVOLVED IN THE PRODUCTION OF FLORAL SCENT IN CLARKIA-BREWERI

S-Linalool is one of the volatiles emitted by Clarkia breweri Grey [Gr een] flowers to attract its moth pollinator. S-Linalool synthase, the enzyme that stereoselectively converts the ubiquitous C-10 intermediat e GPP to S-linalool, is abundant in stigmata of freshly opened flowers , and it was purified to >95% homogeneity by anion-exchange and hydrox yapatite chromatography. S-Linalool synthase is operationally soluble as are other monoterpene synthases, has a K-m of 0.9 mu M for geranyl pyrophosphate, exhibits a strict requirement for a divalent metal cofa ctor with a preference for Mn2+ (K-m = 45 mu M), and shows an optimal pH of 7.4. The enzyme is active as a monomer of 76 +/- 3 kDa as determ ined by gel permeation chromatography and polyacrylamide gel electroph oresis. Neither S- nor R-linalyl pyrophosphates are substrates for the C. breweri S-linalool synthase, although this tertiary allylic pyroph osphate ester is a bound intermediate in the biosynthesis of cyclic mo noterpenes from geranyl pyrophosphate in many plant species, where it also serves as an alternate substrate. (C) 1995 Academic Press, Inc.