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 |