Abstract: The present invention cloned a cDNA clone encoding isopentenyl diphosphate (hereafter “IPP”) isomerase (EC 5.3.3.2) from a cDNA library of Hevea brasiliensis latex. The clone has a continuous open reading frame encoding a peptide of 234 amino acids with a predicted molecular mass of 26.7 kDa. The deduced protein is acidic with an isoelectric point of 4.7 and shows high sequence identity with other IPP isomerases. The recombinant protein expressed in Escherichia coli showed IPP isomerase activity. In vitro rubber biosynthesis assays using washed rubber particle (WRP) deprived of initiating allylic diphosphates were performed with the addition of IPP isomerase in the reaction mixture. Results revealed that the recombinant IPP isomerase is catalytically active in catalyzing the conversion of IPP to DMAPP, a key activation step of the basic five-carbon isoprene unit in rubber biosynthesis. Southern analysis indicated that the IPP isomerase is encoded by two genes in Hevea rubber tree.

Abstract: Natural rubber products are made from fig tree (Ficus carica) by homogenizing the plants in an acetone/benzene and separating the rubber-containing phase by centrifugation. F. carica contains about 4% (w/v) natural rubber in latex, and 0.3, 0.1 and 0.1 % in bark, leaf and fruit, respectively. Molecular mass of the natural rubber from F. carica is about 128 kD. The latex serum of F. carica contains only a small numbers of proteins, with a 48 kD and a 25 kD protein as major proteins. Similar to Hevea brasiliensis and Parthenium argentatum Gray, proteins participating in rubber biosynthesis of F. carica are tightly associated with the rubber particles. Natural rubber is made using the latex serum and the proteins in latex, leaf, bark, and fruit of F. carica.