Magnesium ion regulation of in vitro rubber biosynthesis by Parthenium argentatum Gray

Natural rubber is produced by a rubber transferase (a cis-prenyltransferase). Rubber transferase uses allylic pyrophosphate to initiate the rubber molecule and isopentenyl pyrophosphate (IPP) to form the polymer. Rubber biosynthesis also requires a divalent metal cation. Understanding how molecular weight is regulated is important because high molecular weight is required for high quality rubber. We characterized the in vitro effects of Mg2+ on the biosynthetic rate of rubber produced by an alternative natural rubber crop, Parthenium argentatum (guayule). The affinity of the rubber transferase from P. argentatum for IPP (.) Mg was shown to depend on the Mg2+ concentration in a similar fashion to the H. brasiliensis rubber transferase, although to a less extreme degree. Also, in vitro Mg2+ concentration significantly affects rubber molecular weight of both species, but molecular weight is less sensitive to Mg2+ concentration in P. argentatum than in H. brasiliensis. (c) 2006 Elsevier Ltd. All rights reserved.