Source Year: 1997

Bottom fraction (BF) separated from fresh Hevea latex by untracentrifugation, after pre-incubation at 4 degree C overnight, produced new rubber on incubation at 37 degree for 6 h. Rubber yield was increased about 3.2- and 4.7- fold by the addition of isopentenyl diphosphate (IDP) or farnesyl diphosphate (FDP), respectively. Rubber formed on incubation in the presence of FDP showed a clearly bimodal MW distribution with MW lower than that of endogenous rubber. This indicated that the formation of new rubber in BF uses FDP as a direct initiator. The presence of the dimethylallyl-group of the initiating species was observed in new rubber formed on incubation of fresh BF with FDP, although it was not detected in in vivo rubber. New rubber contained no long-chain fatty acid groups esterified to the rubber molecules as observed in in vivo Hevea rubber.