Toward total elucidation of biosynthetic mechanism of natural rubber

Natural rubber (NR), mainly consisting of cis-1, 4-polyisoprene with a few trans-isoprene units at the ω-terminus, is a non-fungible natural polymer used for manufacturing rubber products such as tyres because of its unique physical properties. Industrial NR production depends solely on latex, the cytoplasm of laticifers in vascular tissues, from the Para rubber tree (Hevea brasiliensis). In latex, NR exists as the rubber particle (RP), which is a specialized organelle, and primarily consists of a hydrophobic rubber core enclosed by a lipid monolayer. To meet the ever-increasing demand for NR, molecular breeding and metabolic engineering of H. brasiliensis for improvement of the NR production are required. Here, we review molecular mechanisms for the NR biosynthesis elucidated so far. Recent important progress in the functional identification of key enzymes in the NR biosynthetic pathway enables us to synthesize extraordinary long-chain polyisoprenoids corresponding to NR in vitro by using the NR biosynthetic machinery reconstituted on RPs.