Significant Role of Bacterial Undecaprenyl Diphosphate (C₅₅‐UPP) for Rubber Synthesis by Hevea Latex Enzymes

Abstract

Washed bottom fraction (BF) membrane-bound particles of centrifuged fresh Hevea latex were found to be very active in rubber biosynthesis (RB). The washed BF membrane (WBM) showed higher RB activity and is strongly stimulated by anionic surfactants--more by DOC than SDS. WBM enzymes system can synthesize rubber either with allylic isoprenes (higher RB) or without (lower RB). Washed rubber particles (WRP), used generally in RB assays, had very low RB activity compared to the much higher activity observed for WBM. Bacterial undecaprenyl diphoshate (C(55)-UPP) was very active allylic initiator for rubber synthesis by WBM. Comparisons of allylic UPP with the shorter ones (C(15)-FPP, C(20)-GGPP) showed that UPP was the most effective. WBM activity orders were UPP >> GGPP > FPP. The DOC activated WBM synthesized less polyprenyl intermediates (butanol extractable) but more final rubber product (toluene/hexane extract), different than FPP and GGPP. WBM enzymes were highly versatile in using diverse different allylics, but UPP was most preferable. WRP was found a little active for UPP with DOC, but still much lower than WBM. Rubber product analysis by RP-TLC with acetone/hexane solvent system showed that WBM was mostly rubber, but WRP was mainly the intermediates. Quantitative analysis showed that WBM labeled rubber was confined to the origin spot, different than WRP as mainly labeled intermediates. It was thus confirmed that the WBM plays the key role in RB functions, and not WRP as mostly reported. WBM served as the actual rubber synthesis site, and bacterial UPP was very good RB initiator.

Multi‐scaled microstructures in natural rubber characterized by synchrotron X‐ray scattering and optical microscopy

“…The mechanism of the biosynthesis of NR molecules is still not completely understood since the initiation, growth, and termination processes are complicated, and many different kinds of proteins are involved. Although various polymerization mechanisms have been proposed,4, 16–18 it is now confirmed that the polymerization occurs at enzyme proteins on the surface of the membranes surrounding the rubber particles. Therefore, several kinds of proteins exist in the NR latex, and many of them remain in the raw rubber.…”

Draft genome sequence of the rubber tree Hevea brasiliensis

“…In the H. brasiliensis genome, we identified 18 genes encoding enzymes for the MVA pathway and 29 for the MEP pathway. For the initiation of rubber biosynthesis, a priming allylic diphosphate (farnesyl diphosphate, geranylgeranyl diphosphate, or undecaprenyl diphosphate) is needed [36]. The biosynthetic pathway leading to these compounds involves 5 enzymatic steps encoded by 21 genes in the assembly.…”