Analysis of Biosynthesis Mechanism Associated with Molecular Structure of Natural Rubber

研究了天然橡胶的生物合成机理与分子结构的关系。通过加入FDP和IDP，在通过超离心从天然胶乳分离的底部馏分的存在下，橡胶分子聚合。体外合成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存在的顺式-1，4-聚异戊二烯。通过对天然胶乳进行粒径分级，研究了胶乳粒径与链伸长的关系。用~（14）C-IDP、~（14）C-IDP +FDP和~（140）-IDP+GGDP对胶乳进行了热处理，结果表明，胶乳的链增长和链终止与胶乳的粒径有关。用核磁共振、X射线衍射和粘度计对小粒径和大粒径的橡胶进行了表征。由小橡胶颗粒凝聚而成的橡胶是末端带有活性磷酸基团的线型分子。而大橡胶颗粒中的橡胶则是以磷脂为末端的支链分子，磷脂与脂肪酸相连。研究了在底部组分存在下橡胶分子的体外合成机理，证明了IDP合成酶等酶和碳源的存在。通过分析体外合成前后底物的组成来确定碳源。

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.