TRICHODIENE SYNTHASE - SUBSTRATE-SPECIFICITY AND INHIBITION

The substrate specificity of the sesquiterpene synthase trichodiene sy nthase was examined by determining the V-max and K-m parameters for th e natural substrate, trans, trans-farnesyl diphosphate (1), its stereo isomer, cis,trans-farnesyl diphosphate, and the tertiary allylic isome r, (3R)-nerolidyl diphosphate (3), using both the native fungal and re combinant enzymes. A series of farnesyl diphosphate analogs, 15, 16, 2 0, 7, 8, and 9, was also tested as inhibitors of trichodiene synthase. 10-Fluorofarnesyl diphosphate (15) was the most effective competitive inhibitor, with a K-I of 16 nM compared to the K-m for 1 of 87 nM, wh ile the ether analog of farnesyl diphosphate, 8, an extremely potent i nhibitor of squalene synthase, showed only modest inhibition of tricho diene synthase, with a K-I/K-m of 70.