IMMUNOINHIBITION OF RUBBER PARTICLE-BOUND CIS-PRENYL TRANSFERASES IN FICUS-ELASTICA AND PARTHENIUM-ARGENTATUM

A cis-prenyl transferase ('rubber transferase') catalyses the polymerization of isoprene units, derived from isopentenyl diphosphate, into natural rubber (cis-1,4-polyisoprene). Cis-prenyl transferase activity is firmly associated with cytoplasmic rubber particles but the membrane-bound enzyme has yet to be identified. We have compared two different species, Ficus elastica and Parthenium argentatum, which produce predominantly short chain and long chain rubber, respectively. The two species have disparate rubber particle protein complements. Antigenic similarities between the rubber particle proteins may include their cis-prenyl transferases, which likely contain some structural features in common. Cis-prenyl transferase activity in F. elastica rubber particles was specifically inhibited by affinity-purified polyclonal IgG raised against a protein (LPR) purified from F. elastica rubber particles. Thus, LPR appears to contain the cis-prenyl transferase active site. Anti-LPR IgG also specifically inhibited cis-prenyl transferase activity in rubber particles from P. argentatum. Thus, an anti-LPR IgG recognized similar epitopes at or near the active site of both the F. elastica and P. argentatum cis-prenyl transferases. This is the first time that an antibody to a rubber particle protein has been shown to specifically inhibit cis-prenyl transferase activity, and could lead to the isolation of the enzyme from P. argentatum.