Analysis of Biosynthesis Mechanism Associated with Molecular Structure of Natural Rubber

研究了与天然橡胶分子结构相关的生物合成机理。用超速离心法从天然胶乳中分离出底部馏分，通过加入FDP和IDP聚合橡胶分子。体外合成的橡胶分子的结构表征表明，天然橡胶的引发物种不同于其他天然生成的顺-1，4-聚异戊二烯。终止步骤被认为是天然橡胶所特有的。对天然胶乳进行了粒度分级，以考察链长与粒度的关系。胶乳分别与14C-IDP、14C-IDP+FDP和140-IDP+GGDP共孵育，胶乳的链长和终止与胶乳的粒径有关。用核磁共振、GPO和粘度计对小粒径和大粒径橡胶进行了表征。由橡胶小颗粒凝聚而成的橡胶是含有活性末端磷酸基团的线型分子。相反，从大颗粒橡胶中得到的橡胶是以磷脂与脂肪酸相连的支化分子。为了证明IDP合成酶和碳源的存在，研究了底馏分存在下橡胶分子的体外合成机理。通过对体外合成前后底馏分组成的分析，确定了碳源。

Biosynthesis mechanism associated with molecular structure of natural rubber was investigated. The rubber molecule was polymerized by the addition of FDP and IDP in the presence of the bottom fraction isolated from natural rubber latex by ultra-centrifugation. The structural characterization of in-vitro synthesized rubber molecule showed that the initiating species of natural rubber was different from those of the other naturally occurring cis-1,4-polyisoprene. The termination step was presumed to be specific for natural rubber.The natural rubber latex was fractionated in particle size to investigate the relationship between chain elongation and particle size. The latex was incubated with 14C-IDP, 14C-IDP+FDP and 140-IDP+GGDP.The chain elongation and termination of the rubber was related to the particle size of the latex. The rubber in the small and large particle size was characterized by NMR, GPO and viscometry. The rubber coagulated from small rubber particle was linear molecule which has a living terminal phosphoric acid group. In contrast, the rubber from large rubber particle was branched molecule terminated with phospholipid linked to fatty acid.The mechanism of in-vitro synthesis for rubber molecule in the presence of bottom fraction was investigated to prove the presence of enzyme such as IDP synthase and carbon sources. The carbon source was identified by analyzing composition of bottom fraction before and after the in-vitro synthesis.