Studies on enzymes concerned in the biosynthesis of large amounts of useful isoprenoids by a green microalga

绿色微藻巴西芽孢杆菌产生大量液态碳氢化合物，有望成为一种可再生能源。根据产生的碳氢化合物类型，将该藻类划分为A、B和L三个化学小种。B族产生大量的三萜碳氢化合物。所有的萜类都是由通用的前体异戊烯基二磷酸(IPP)和二甲基烯丙基二磷酸(DMAPP)生物合成的。藻类产生的三萜类化合物是由前体特异性合成的，这些前体不是甲氧戊酸途径，而是“非甲氧丙戊酸(DOXP/MEP)”途径。我们试图分离催化DOXP/MEP途径中第一反应的1-脱氧-D-木糖-5-磷酸合成酶(DXS)的cDNA克隆。为了了解布氏杆菌产烃的机制，并获得了三个不同的克隆，这些基因都编码有活性的DXS蛋白。该藻类重组DXS蛋白的动力学参数与高等植物的没有显著差异。当藻类活跃地产生三萜时，三种DXs的mRNA水平都很高。

A green microalga Botryococcus braunii produces a large amount of liquid hydrocarbons that are promising as a renewable energy source. This alga is classified into three chemical races A, B, and L by the type of hydrocarbon produced. The B race produces a large amount of triterpene hydrocarbons. All terpenes are biosynthesized from the universal precursors, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). The triterpenes produced by the alga are specifically synthesized by precursors derived from not the mevalonate pathway but the "non-mevalonate (DOXP/MEP)" pathway. We tried to isolate cDNA clone of 1-deoxy-D-xylulose 5-phosphate synthase (DXS) that catalyzes the first reaction in the DOXP/MEP pathway. in order to understand the mechanism of hydrocarbon production by B. braunii, and obtained three different clones All of these genes coded active DXS proteins. Kinetic parameters of the recombinant DXS proteins from this alga were not significantly different from those of the higher plants. Levels of mRNA for three DXS were high when the alga actively produces triterpenes.