The Importance of Being Dolichol

Linear, long-chain isoprenoids, polyisoprenoids with the role or function of a particular chain length distribution in a given system.chain lengths greater than thirty carbons, are ubiquitous membrane constituents now known to be involved Polyisoprenoids are found in cells and tissues in a number of different forms.They are present as the free in glycan synthesis.They are present in small amounts (0.1%) relative to glycerol-based phospholipids (1,2,3), alcohol or esterified with acetate or fatty acids.These forms are particularly abundant in mammalian tissues and are thought not to form bilayers, but rather type II lamellar structures (4,5).There are two different such as liver, brain, and kidney (17,18).In dividing cells and in S. cerevisiae the predominant polyisopren-types of polyisoprenoid lipids known -one with all the isoprene units in the polymer unsaturated and one oid is phosphorylated (1,2,3,19).In CHO cells, for example, oligosaccharide-P-P-dolichol is the most abun-with the isoprene unit of the polymer adjacent to the hydroxyl group (alpha isoprene) saturated.In this dant form (40 -50% of total dolichol pool), with dolichyl phosphate, monoglycosylated phosphorylated doli-minireview, I will refer to the former as polyprenol and the latter as dolichol.chols, free dolichol, and esterified dolichol being less abundant (1,2,19).An interesting feature of these polyisoprenoid lipids is that they are not present as a species of a single Glycosylated phosphopolyisoprenoid lipids serve as glycosyl donors, substrates for glycosyl transferases in chain length, but are found in cells as a family of four or five different chain lengths, with one or two chain glycan synthesis, as do sugar nucleotides.The obvious difference in these two types of sugar donors is their lengths predominating.For example, in Chinese hamster ovary (CHO) cells the predominant polyisoprenol solubility and consequently their intracellular location.There are a variety of glycosylated phosphopolyiso-is dolichol with 95 carbons, although dolichols of 85, 90, and 100 carbons are detected (6,7).Most likely this prenoid lipids known, two examples being mannosylphosphoryldolichol (Man-P-dolichol) and N-acetylglu-feature is the result of the mechanism of action of the biosynthetic enzyme, cis-prenyl transferase, that con-cosaminylpyro-phosphorylundecaprenol (GlcNAc-P-Pundecaprenol).Sugar nucleotides and glycosylphosph-denses isoprenyl units of isoprenyl pyrophosphate onto farnesyl pyrophosphate to a distribution of chain oryllipids are similar in that the linkage broken during the transfer of a glycose moiety in both cases is the lengths (8).The chain length of the major form of prenol varies phosphoglycosidic bond, generating NDP (or CMP in the case of CMP-sialic acids) or phosphopolyisoprenoid from 55 carbons in eubacteria (9,10), 55 and 60 in Trypanosoma (11), 80 and 85 in Drosophila (12), 75 and 80 lipid.During the transfer of a phosphoglycose moiety, the linkage broken is the pyrophosphoryl bond, gener-in Saccharomyces cerevisiaei (13), 85 in Schizosaccharomyces pombe (14), 95 in hamsters (6,7) to 100 carbons ating NMP or phosphopolyisoprenoid lipid, since in this latter case these reactions involve glycosylated pyro-in pigs and humans (15).Prenols in plants range from 40 to 110 carbons; some species of plants have two phosphopolyisoprenoid lipids.In addition to being a sugar donor, phosphorylated classes of polyisoprenols, those of 80 to 110 carbons and a second distribution of prenols up to 200 carbons polyisoprenoid lipids can serve as carriers of oligosaccharide units as they are being assembled before trans-in length (16).As yet, no mutant has been described that results in an alteration of the chain length of a fer.For example, in eukaryotic systems a specific oligosaccharide is preassembled on dolichyl pyrophosphate polyisoprenol.Therefore, we have no understanding of