Polyprenyl phosphates synthesis

For the study of polyprenyl glycosyl phosphates as intermediates in the synthesis of complex glycans, several techniques have been developed, and these have been described elsewhere in detail.18 20 Two important features should be emphasized. First, the very small amounts of polyprenyl phosphates that are present in most tissues for this reason, the use of radioactive techniques for the detection of products is obligatory. Second, on account of the hydrophobic nature of these compounds, and as the enzymes involved in the reactions are membrane-bound, the use of detergents and organic solvents becomes necessary. 

Birault, V., Pozzi, G., Plobeck, N. et al. (1996). Di(polyprenyl) phosphates as models for primitive membrane constituents synthesis and phase properties. Chemistry - a European Journal, 2, 789-99. 

The formation of lipid-linked sugars in vitro by Bacillus stearothermophilus. Salmonella typhimurium, and Shigella jlexneri requires an unsaturated a-isoprenyl residue in a polyprenyl phosphate, in contrast to th- t in rat-liver microsomes which requires a saturated a-isoprenyl residue. o-Glucopyranosyl polyprenyl phosphate was formed on incubation of UDP-D-[ C]glucose with particulate preparations from B. stearothermophilus, and it may serve as a D-glucosyl donor in the synthesis of an extracellular polysaccharide. The properties of the membrane-associated sialyltransferase complexes of Escherichia coli have been examined. These complexes catalyse the incorporation of iV-acetylneuraminic... 

FIGURE 8.18 Dolichol phosphate is an initiation point for the synthesis of carbohydrate polymers in animals. The analogous alcohol in bacterial systems, undecaprenol, also known as bactoprenol, consists of 11 isoprene units. Undecaprenyl phosphate delivers sugars from the cytoplasm for the synthesis of cell wall components such as peptidoglycans, lipopolysaccharides, and glycoproteins. Polyprenyl compounds also serve as the side chains of vitamin K, the ubiquinones, plastoquinones, and tocopherols (such as vitamin E). 

Thiamin is synthesized in bacteria, fungi, and plants from 1-deoxyxylulose 5-phosphate (Eq. 25-21), which is also an intermediate in the nonmevalonate pathway of polyprenyl synthesis. However, thiamin diphosphate is a coenzyme for synthesis of this intermediate (p. 736), suggesting that an alternative pathway must also exist. Each of the two rings of thiamin is formed separately as the esters 4-amino-5-hydroxy-methylpyrimidine diphosphate and 4-methyl-5-((i-hydroxyethyl) thiazole monophosphate. These precursors are joined with displacement of pyrophosphate to form thiamin monophosphate.92b In eukaryotes this is hydrolyzed to thiamin, then converted to thiamin diphosphate by transfer of a diphospho group from ATP.92b c In bacteria thiamin monophosphate is converted to the diphosphate by ATP and thiamin monophosphate kinase.92b... 

Insertion of monomer units at the base of a chain is a major mechanism of polymerization that is utilized for synthesis not only of polysaccharides but also of proteins (Chapter 29). For most carbohydrates the synthesis is dependent upon a polyprenyl lipid alcohol, hi bacteria this is often the 55-carbon undecaprenol or bactoprenol,136 which functions as a phosphate ester ... 

The first stage of the synthesis is the preparation of the substrate for enzymatic polymerization, the polyprenyl pyrophosphate-galactosy1-rhamnosy1-mannose XXI. Since the most convenient way to control the polycondensation reaction is the use of isotopic methods, a procedure for incorporation of tritium into trisaccharide I was developed (2 5). Labelled trisaccharide was then converted into the glycosyl phosphate XIX through interaction of its peracetate III with anhydrous phosphoric acid (26). Conditions were found under which the reaction is accompanied by minimal destruction and yields the Ot-phosphate of the trisaccharide. 

The synthesis of XXI was accomplished by direct condensation of XIX with moraprenyl phosphoimidazo1id-ate XX in a THF-DMSO-mixture under mild conditions (27). This new method makes it possible to prepare polyprenyl pyrophosphate oligosaccharides directly from unprotected phosphates of oligosaccharides, thus avoiding the need for de-protection procedures which may be accompanied by extensive destruction of polyprenyl pyrophosphate sugars. 

L. L. Danilov, S. D. Maltsev, V. N. Shibaev, and N. K. Kochetkov, Synthesis of polyprenyl pyrophosphate sugars from unprotected mono- and oligo-saccharide phosphates, Carbohydr. Res., 88 (1981) 203-211. 

The existence of mannosylated saccharides linked to dolichol via a pyrophosphate was already well established. Studies by Behrens etal. (1973) had shown that rat liver microsomes could catalyse the synthesis of various lipid-linked oUgosaccharides from GDP mannose and dolichol phosphate, among which were some that were soluble in chloroform-methanol-water (1 1 0.3, v/v). These were more polar than dolichol monophosphate derivatives and could be bound to DEAE-cellulose in the presence of the organic solvent. In an ammonium formate gradient (also in the organic solvent) these polyprenyl saccharides eluted at the position of dolichol pyrophosphate derivatives. Waechter et al (1973) independently showed that a similar class of compounds was produced from GDP-[ C]maimose in the presence of microsomes from hen oviduct and that the labelled products... 

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