English Abstract

Molecular Insights of Natural Rubber Biosynthesis-An Approach from Prenyltransferase Gene Analysis Seiji Takahashi Tanetoshi Koyama Institute of Multidisciplinary Research for Advanced Materials Tohoku University, Miyagi,Japan Nippon Gomu Kyokaishi,(2003),76(12), 446-452 General Review in Japanese. Abstract Linear prenyl diphosphates whose carbon chain length varies widely from geranyl diphosphate (C10) to natural rubber are biosynthesized by the catalytic function of a group of enzymes called prenyltransferases. Prenyltransferases are classified in two major groups, trans- or (E)-prenyltransferases and cis- or (Z)-prenyltransferases. From the year of 1987, many genes encoding (E)-prenyltransferases have been cloned and characterized well. However, the structure and detailed mechanism of (Z)-prenyltransferase had been completely unknown until our identification of a gene encoding the undecaprenyl diphosphate synthase (UPS) from Micrococcus luteus B-P 26. Not only the primary structure but also the tertiary structure of the UPS is quite different from those of (E)-prenyltransferases. Multiple alignment of primary structures of (Z)-prenyltransferases identified from various organisms reveals that there are five highly conserved regions among (Z)-prenyltransferases. In order to elucidate the biosynthetic pathway of natural rubber which is composed of cis-1,4-polyisoprene, we isolated and characterized two genes encoding (Z)-prenyltransferases from the latex in Hevea brasiliensis by using sequence information on the conserved regions of (Z)-prenyltransferases. In vitro rubber transferase assay using the recombinant gene product revealed that the enzyme catalyzed the formation of polyprenyl products with approximate sizes around Da. Moreover, in the presence of washed bottom fraction from latex, the rubber transferase activity and the size of the major product was increased, suggesting a possible requirement of certain activation factors in the washed bottom fraction for the production of high molecular weight rubber. Keywords: Isoprenoid, Hevea brasiliensis, Prenyltransferase, Rubber transferase

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