The stereochemistry of rubber biosynthesis

The stereochemistry of the formation of natural rubber and trans-trans-farnesyl pyrophosphate in latex has been studied in vitro using [2-14C-(4R)-4-3H1] and [2-14C-(4S)-4-3H1]mevalonates as substrates. The proton eliminated from C-2 of isopentenyl pyrophosphate during the formation of farnesyl pyrophosphate in latex has the same steric position as that released in the liver system, and is epimeric with that eliminated during the biosynthesis of rubber. Complete stereospecificity is exhibited by the enzymes in the two cases. In rubber biosynthesis isoprene residues are incorporated directly in an all-cis configuration without the intervention of trans structures.