Y-Humulene

Steele C. L., Crock J., Bohlmann J. and Croteau R. (1998) Sesquiterpene synthases from grand fir (Abies grandis) comparison of constitutive and wound-induced activities, and cDNA isolation, characterization and bacterial expression of 8-selinene synthase and y-humulene synthase. J. Biol. Chem. 273, 2078-2089. 

Consistent with the participation of arginine residues in diphosphate orientation and ionization by monoterpene and sesquiterpene synthases [91,117] is the substitution of a highly conserved RxR motif by RxC in y-humulene synthase (residues 306-308). Perhaps this substitution in y-humulene synthase perturbs diphosphate binding in much the same way as was suggested for the central arginine mutation in the DRRYR motif of trichodiene synthase which resulted in multiproduct formation [117]. 

In accord with the high level of sequence similarity between d-selinene synthase and y-humulene synthase, all carbocation deprotonations result by abstraction from a hmited number of common carbon atoms (Scheme 12 and 13). It is Hkely that a single active site base can mediate deprotonations from spatially adjacent carbon atoms of these carbocationic intermediates. In the case of... 

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