P15.17: The pyrophosphate leaving group in the cyclopropane-forming part of the squalene synthase reaction is protonated by an active site tyrosine that is positioned close to C 1 of one of the FPP mo...P15.17: The pyrophosphate leaving group in the cyclopropane-forming part of the squalene synthase reaction is protonated by an active site tyrosine that is positioned close to C 1 of one of the FPP molecules. C15.6: The biosynthesis of valine begins with the condensation of two molecules of pyruvate (with the assistance of a certain coenzyme), followed by an acyloin rearrangement to form the intermediate shown below.
