REGULATION IN BIOSYNTHESIS OF CHLOROPHYLL IN CHLOROPLAST OF CULTURED CELLS OF LIVERWORT

叶绿体萜类化合物长期以来被认为是通过甲羟戊酸利用途径生物合成的。然而，它们最近被证明是通过非甲羟戊酸介导途径生物合成的。本研究的目的是为了证明在livewort叶绿体中形成类异戊二烯的优先标记机制，并证明甲羟戊酸利用途径和非甲羟戊酸介导途径同时运作。我也证实了醋酸同化参与叶绿体萜类化合物的生物合成。将^2H-和^<13> c标记的乙酸、甘油和葡萄糖投喂到扁平扁豆的悬浮培养中，以验证非甲羟戊酸途径和乙酸同化参与了叶绿体萜类的形成。为了阐明fpp来源部分的优先标记机制，我们从培养的扁平扁豆细胞制备的原生质体中分离出叶绿体。并与…More未标记、^3H和^<14>C标记的甲戊酸盐、二磷酸异戊烯酯（IPP）和FPP孵育。含有[6,6-^2H_2]-葡萄糖和[2-^<13>C]-甘油的植基侧链的标记模式表明，非甲羟酸途径参与了植基侧链的生物合成。包含标记醋酸酯的植基侧链的标记模式证明了两个重要的结果，即(1)完整的醋酸酯在形成甲羟戊酸之前被分解。醋酸酯要么由两个甲基碳重整，要么由两个羧基碳重整。甲羟戊酸是由重组的醋酸酯形成的，(2)这些发现表明甲羟戊酸也在叶绿体中形成。乙酸经三羧酸循环、还原性戊糖磷酸循环和乙醇酸途径连续几代同化。放射性同位素标记的FPP有效地结合到叶绿体中，并非常迅速地转化为香叶基和叶基片段，而标记的甲羟戊酸与这些化合物的结合程度较低。这些结果表明，叶绿体可以直接（或间接）吸收FPP，然后将其转化为香叶酰二磷酸（GGPP）。甲羟戊酸可能以极低的水平进入叶绿体，但可以在叶绿体内代谢为GGPP。它们也确实表明，FPP衍生部分的优先标记是由叶绿体直接（或间接）摄取FPP引起的。少

Chloroplastidic terpenoids were believed for long time to be biosynthesized via mevalonate utilizing pathway. They have, however, very recently been proven to be biosynthesized via non-mevalonate mediating pathway. The objectives of this research are to demonstrate a mechanism of preferential labelling in the formation of isoprenoids within chloroplasts of livewort and to prove a simultaneous operation of mevalonate utilizing pathway and non-mevalonate-mediating pathway. I also verified involvement of acetate assimilation in biosynthesis of chloroplastidic terpenoids.The ^2H- and ^<13>C-labelled acetate, glycerol and glucose were fed to the suspension cultures of H.planus to verify involvement of non-mevalonate pathway and acetate assimilation in the formation of chloroplastidic terpenoids. To elucidate the mechanism of the preferential labelling of the FPP-derived portion, we isolated chloroplasts from protoplasts which are prepared from cultured cells oh H.planus. and incubated with … More non-labelled, and ^3H and ^<14>C labelled mevalonate, isoprenyl diphosphate (IPP) and FPP.Labelling patterns of the phytyl side chain incorporating [6,6-^2H_2]-glucose and [2-^<13>C]-glycerol indicated that non-mevalonate pathway involves the biosynthesis of the phytyl side chain. Labelling patterns of the phytyl side chain incorporating labelled acetate demonstrate two important results, i.e. (1) intact acetate was decomposed prior to the formation of mevalonate. Acetate was reformed either from two methyl carbons or two carboxy carbon. Mevalonate was formed from the reformed acetate, and (2) these findings suggest that mevalonate was also formed in chloroplasts. And acetate was assimilated by a consecutive passages of TCA cycle, reductive pentose phosphate cycle and glycolic path way.Radioisotopically labelled FPP was effectively incorporated into chloroplasts and converted to geranylgeranyl moiety and phytyl moiety very rapidly, while labelled mevalonate was incorporated to these compounds to a less extent. These results indicated that chloroplasts can take in FPP directly (or indirectly) and then convert it to geranylgeranyl diphosphate (GGPP). While mevalonate might be incorporated into chloroplasts at very low level but it can be metabolized to GGPP within chloroplasts. They also indeed indicate that the preferential labelling of the FPP-derived portion was caused by direct (or indirect) uptake of FPP by chloroplasts. Less