Biosynthetic Mechanism of Unique Lipids Constituting Archaebacterial Cell-Membrane

进化上有趣的古细菌含有2，3-二-OMICRON-聚异戊二烯基甘油结构作为核心膜脂质，其可被视为真细菌和真核细胞脂质的镜像。本研究通过稳定同位素示踪技术和核磁共振分析，对膜脂的立体化学合成机制进行了研究。1）通过对1，2-和2的立体专一性合成，证实了嗜盐古细菌Halobacterium halobium核心脂质甘油部分的绝对立体化学，3-二-OMICRON-植烷基甘油的合成及其500 MHz ~ 1H-NMR谱分析。首次从立体化学的角度阐明了卤代物的结构。核心脂质似乎是由甘油和D-葡萄糖通过还原磷酸二羟丙酮或其衍生物生物合成的，在此过程中， ...更多信息 C-2的立体化学是颠倒的。在醚键形成中，甘油的C-2和C-3氧原子充当亲核试剂。3）基于手性转录的概念，利用1，2：5,6-二-OMICRON-碘亚丙基-α-D-呋喃己糖-3-脲为模板。4）首次通过追踪D-[5-（4-甲基-4-氧代-5-氧代-5-氧代-6-氧代-6-氧代-6-碘亚丙基]-α-D-呋喃己糖-3-脲的氘，2 H]-和D-[4- ^2H]葡萄糖，然后用500 MHz 1H-NMR比较氘代脂质和合成的sn-2，3-二-OMICRON-植烷基（3R）-和-（3S）-[3- ^2H_1]甘油。嗜热嗜酸古菌Sulfolobus acidocaldarius的二甘油四醚脂质是由甘油不经转化合成的在C-2位的构型表明，可能直接形成甘油-1-磷酸，而不是在H中发现的甘油-3-磷酸。盐生菌。在古细菌种内可能进化出多样化和对比鲜明的生化转化。少

Evolutionary intriguing archaebacteria contain 2, 3-di-OMICRON-polyisopranyl glycerol structures as core membrane lipids, which may be regarded as mirror images to the lipids of the eubacterial and eukaryotic cells. In this project, the biosynthetic mechanisms which afford such intriguing stereochemistry of the membrane lipids were studied by the stable isotope-tracer technique and NMR analysis.1) The absolute stereochemistry of the glycerol moiety of core lipid in halophilic archaebacteria Halobacterium halobium was confirmed by combination of the enantiospecific synthesis of both 1, 2- and 2, 3-di-OMICRON-phytanyl glycerol from D-mannitol and close analysis of their 500MHz ^1H-NMR spectra.2) The biosynthesis of 2, 3-Di-OMICRON-phytanyl glycerol in H. halobium has been elucidated for the first time from the stereochemical viewpoints. The core lipid appears to be biosynthesized from glycerol and D-glucose via reduction of dihydroxyacetone phosphate or its derivative, during which the s … More tereochemistry of C-2 is inverted. In the ether-bond formations, the C-2 and C-3 oxygen atoms of glycerol act as nucleophile. The plausible pathway of the biosynthesis was postulated.3) A novel and convenient synthetic method of chirally monodeuterated glycerol was developed based on the chirality transcription concept using 1, 2 : 5, 6-di-OMICRON-iopropylidene-alpha-D-ribo-hexofuranos-3-urose as a template.4) Stereochemistry of the archaebacterial triose-phosphate isomerase reaction was elucidated for the first time by chasing the deuterium of D-[5- ^2H]-and D-[4- ^2H]glucose during the core lipid biosynthesis in Halobacterium halobium, followed by 500 MHz ^1H-NMR comparison of the deuterated lipid and the synthetic sn-2, 3-di-OMICRON-phytanyl (3R) - and - (3S) -[3- ^2H_1]glycerol.5) The finding that the diglyceryl tetraether lipid of thermoacidophilic archaebacteria Sulfolobus acidocaldarius is biosynthesized from glycerol without inversion of configuration at C-2 suggests a possibility of direct formation of glycerol-1-phosphate rather than glycerol-3-phosphate found in H. halobium. A diversified and contrasting biochemical transformation may be evolved within the archaebacterial species. Less