Polyprenols

The Css polyprenol (154) obtained from leaves of Magnolia campbelUi has been shown to be a mixture of cis- and /ran -isomers. The preparation of dolichyl phosphate (155) by a pea cell-free extract has been described. Evidence has been obtained that a lipid, containing 7V-acetylglucosamine, which was obtained from Phaseolus vulgaris hypocotyls, consists of a mixture of the dolichol (156) derivatives dolichyl pyrophosphate N-acetylglucosamine and dolichyl pyrophosphate di-N-acetylchitobiose.  

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Dolichol (from pig liver) [11029-02-0] Cgo-Cios polyprenols. Cryst 6 times from pet ether/EtOH at -20°C. Ran as entity on a paper chromatogram on paraffin impregnated paper, with acetone as the mobile phase. [Burgos Biochem J 88 470 1963.]... 

Long-chain polyisoprenoid. molecules with a terminal alcohol moiety are called, polyprenols. The dolichols, one class of polyprenols (Figure 8.18), consist of 16 to 22 isoprene units and, in the form of dolichyl phosphates, function to carry carbohydrate units in the biosynthesis of glycoproteins in animals. Polyprenyl groups serve to anchor certain proteins to biological membranes (discussed in Chapter 9). 

Solanesol and other prenyl alcohols are important as metabolites in mulberry and tobacco leaves and in the synthesis of isoprenoid quinones. Hence, Sato and collaborators107 have developed a stereoselective synthesis of all-trans-polyprenol alcohols up to C50. Construction of the requisite skeletons was accomplished by the alkylation of a p-toluenesulphonyl-stabilized carbanion, followed by reductive desulphonylation of the resulting allylic sulphonyl group. This was achieved most efficiently by the use of a large excess of lithium metal in ethylamine (equation (43)), although all reaction conditions led to mixtures. The minor product results from double bond rearrangement. 

C. Nucleoside Diphosphate Sugars.—A polyprenol phosphate containing eleven isoprene units is involved in the biosynthesis of various bacterial cell-wall components.As mentioned in last year s Report, another isoprenoid phosphate, dolichol monophosphate (40), is an intermediate in sugar... 

If the synthesis starts from glucose molecules, then the initial step is the transfer of glucose residues from UDP-glucose onto an intermediary acceptor-dolichol phosphate (membrane-bound polyprenol phosphate). Dolichol phosphate assists in the synthesis of an... 

The advantages of supercritical fluid chromatography for polymer separations have been illustrated in the literature for many years. A recent example is the separation of long-chain polyprenols using SFC with matrix-assisted laser-desorption ionization TOF mass spectrometry [10]. The generic name for 1,4-polyprenyl alcohols is polyprenol these compounds generally have smaller polymerization chains of less... 

Fig. 16.4. SFC chromatogram of long-chain polyprenols in E. ulmoides leaves. The sample had Mn 3.99 x 103 (calibrated against cis-l,4-polyisoprene standards) and MJMn 1.41. The numbers in the chromatogram represent degrees of polymerization for polyprenol homologues [10].

Polyprenols and dolichols Vascular plants bacteria animals +... 

Clenbuterol in pork, beef, and hog liver Co(II) ion as 4-(2-thiazolylazo)resorcinol (TAR) or 5-methyl-4-(2-thiazolylazo)resorcinol (5MTAR) total phenols after nitrosation of USEPA classified 11 priority pollutant phenols polyprenol and doUchoP ... 

Bamba, T., Fukusaki, E., Minakuchi, H., Nakazawa, Y, and Kobayashi, A., Separation of polyprenol and dolichol by monolithic silica capillary column chromatography. Journal of Lipid Research 46(10), 2295-2298, 2005. 

Biosynthesis.—Ubiquinone. The identification of 3,4-dihydroxyhexaprenylben-zoate (162) in a Saccharomyces cerevisiae mutant strain that cannot synthesize ubiquinone suggests that (162) may be an intermediate in ubiquinone-6 biosynthesis in eukaryotes, in contrast to the pathway via 2-polyprenylphenol which operates in prokaryotes. In mammalian systems alternative routes have been discussed for ubiquinone biosynthesis in rats." Some properties of mitochondrial 4-hydroxybenzoate-polyprenol transferase have been described."" ... 

Although it could be established that saturation of the a-isoprene unit of polyprenol phosphate is important for these compounds to act as effective acceptors of glycosyl moieties in eukaryotic cells, little chain-length specificity was observed in such studies.39-41 This observation found support in the result that the same set of prenylogs occurs in total-yeast dolichol and in dolichol diphosphate-linked 2-acetamido-2-deoxy-D-glucose synthesized in vitro with yeast-cell homogenates.42 As already noted by Chojnacki and coworkers,40 dur-... 

Ibataet id. [52] isolated long-chain betulaprenol-type polyprenols containing 14 to 22 isoprene units (41) from the ginkgo leaves and determined their structures by mass spectroscopy, H-... 

NMR and 13C-NMR. The concentrations of these polyprenols increased from 0.04 to 2.0% of dry weight with maturation of the leaves. A supercritical fluid chromatographic procedure for the quantitation of polyprenols in the ginkgo leaves was developed by Huh ef al. [53]. 

In abbreviations for polyprenyl glycosyl phosphates, p stands for phosphate, and pp" for diphosphate groups. The abbreviation Bpr means a bacterial undecaprenyl group. For the moraprenyl group (see Ref. 57), the abbreviation Mpr is used, and the symbol Pre stands for any unidentified, lipid acceptor having the properties of polyprenol. 

Readily available plant polyprenols from leaves of ficus (ficaprenol) or mulberry (moraprenol) are frequently used in biosynthetic studies as substitutes for bacterial undecaprenol. These polyprenols are composed of 10-12 isoprenic units (undecaprenol is the main component) with three internal E-isoprenic units localized at the carbon chain.58-59 See This Volume, pp. 341-385. 

The structures of polyprenyl diphosphate-linked intermediates of Salmonella O-specific-polysaccharide biosynthesis were confirmed by chemical synthesis of their analogs derived from the plant polyprenols ficaprenol and moraprenol (structurally related to bacterial polyprenol57) with the following study of their behavior as substrates of enzymic reactions. Synthetic polyprenyl a-D-galactopyranosyl diphosphate291,292 was found to serve as an effective acceptor for the transfer of L-rhamnosyl groups.293"295 Two synthetic, isomeric disaccharide derivatives,292 13 and296 14, were tested as acceptors for enzymic D-mannosyl transfer from GDP-Man, but only the former was found to be an efficient substrate.294... 

It is difficult to identify the lipid moiety as a polyprenol, because of the small amounts present in tissues. Nevertheless, some information can be obtained by using glycosylated lipids labelled in the sugar moiety. The first indication of the presence of polyprenyl glycosyl phosphates comes from study of the properties just mentioned, namely, lability to mild acid, stability to mild alkali, and acidic properties. Information on the polyprenyl nature of the lipid may be obtained by labelling the lipid with radioactive 2,4-dideoxyO-C-methyl-D-g/ycero-pentono-l.S-lactone (mevalonic acid ). 

Polyprenol Source No. of isoprene units No. of double bonds E Z a-Residue References... 

Table I summarizes the plant polyprenols that have been isolated and whose sources and some structural aspects have been characterized. These polyprenols occur in different species as mixtures, differing from each other in one isoprene unit. One or two members of the family are very abundant and normally account for 80% of the total polyprenol content of the plant. Most long-chain polyprenols have Z, E double bonds, the E-isoprene units being adjacent to the -residue and to a variable number of Z residues, depending on the plant (see Table I).

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