Rubber formation by fresh bottom fraction of Hevea latex

The formation de novo of rubber was confirmed by the incorporation of C-14-IDP into rubber by fresh bottom fraction (BF) and C-serum (CS) at 37 degrees for 6 hr after pre-incubation with the substrate at 4 degrees overnight. The incorporation of C-14-IDP and rubber yield were highest in fresh BF. A control experiment with boiled BF showed practically no incorporation of C-14-IDP, although it contained about 1% (w/w dried BF) of rubber corresponding to pre-existing rubber. A very small amount of rubber was formed on incubation of CS and C-14-IDP. Rubber formation in fresh BF was inhibited by the addition of NaF. Freeze-dried BF formed no rubber, although it was able to form polyprenols. The radiolabelled rubber formed on incubation of fresh BF and C-14-IDP showed a molecular-weight distribution (MWD) having a peak similar to the low molecular-weight fraction of the skewed unimodal distribution of the endogenous rubber. Membrane-bound particles in fresh BF are presumed to have an important role in the synthesis of new rubber molecules. (C) 1997 Elsevier Science Ltd.