da Costa Bernardo M T, Keasling Jay D, McMahan Colleen M, Cornish Katrina
Department of Chemical Engineering, University of California, Berkeley, CA 94720-3224, USA.
Phytochemistry. 2006 Aug;67(15):1621-8. doi: 10.1016/j.phytochem.2006.04.010. Epub 2006 Jun 15.
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 Mg(2+) 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 Mg(2+) concentration in a similar fashion to the H. brasiliensis rubber transferase, although to a less extreme degree. Also, in vitro Mg(2+) concentration significantly affects rubber molecular weight of both species, but molecular weight is less sensitive to Mg(2+) concentration in P. argentatum than in H. brasiliensis.
天然橡胶由橡胶转移酶（一种顺式异戊烯基转移酶）产生。橡胶转移酶利用烯丙基焦磷酸启动橡胶分子，并利用异戊烯基焦磷酸（IPP）形成聚合物。橡胶生物合成还需要二价金属阳离子。了解分子量是如何调节的很重要，因为高质量的橡胶需要高分子量。我们表征了Mg(2+)对另一种天然橡胶作物银胶菊（银胶菊）产生的橡胶生物合成速率的体外影响。银胶菊橡胶转移酶对IPP.Mg的亲和力显示出与巴西橡胶树橡胶转移酶类似的方式依赖于Mg(2+)浓度，尽管程度没那么极端。此外，体外Mg(2+)浓度显著影响这两个物种的橡胶分子量，但银胶菊的分子量对Mg(2+)浓度的敏感性低于巴西橡胶树。
