Hopanoid from Eubacteria

The new C-labelling pattern of plastidic isoprenoids of Lemna (C-1 and C-5 of IPP from [l- C]glucose) was found earlier in some eubacteria (triterpenic hopanoids, prenyl side chain of ubiquinone) and in Scenedesmus obliquus in the isoprenic units of phytol, B-carotene, lutein, plastoquinone-9 and in the three main sterol components (4). We now found this labelling pattern also in another green alga, Chlorella fusca, grown on [l- C]glucose for the plastidic B-carotene, phytol and for the sterols (see also ref 6). 

This classification has a number of weaknesses. Some bacteria, for example, accept the zoosterol cholesterol from the host animals and use it as a component of membranes, some types of prokaryotic organisms even synthesise sterols de novo, some eubacteria (species of the genus Methylobacterium and Methylosphaera) synthesise 4-methylsterols and 4,4-dimethylsterols (including lanosterol). In many species of bacteria the so-called hopanoids, pentacychc... 

Bacterial isoprenoid synthesis - the Rohmer pathway Current biosynthetic evidence indicates that the steps from IPP to isoprenoids in Eubacteria are the same as those in eukaryotes [62-69] (see [70-73] for literature). Especially the incorporation of C-labeled precursors into prokaryotic hopanoids, sterol surrogates in bacterial membranes (see [73] and literature cited therein), or into ubiquinone-8 [70] has revealed that the classic pathway of IPP formation starting from acetyl-CoA via acetoacetyl-CoA, HMG-CoA, MVA, MVA-P, and MVA-PP does not exist in a great variety of bacteria, including E. coli Zymomonas mobilis, Methylobacterium organophilum, Rhodopseudomonas palustris, R. acidophila, Acetobacter aceti ssp. xylinum, but also in the thylakoids of the cyanobacterium Synechocystis sp. [74]. 

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