The plurality of long chain isoprenoid alcohols (polyprenols) from natural sources

Dolichol deposition in developing mammalian brain: content of free and fatty-acylated dolichol and proportion of specific isoprenologues

Dolichol serves a critical role in N-linked glycoprotein synthesis as the carrier of saccharide moieties. In this study the deposition of dolichol was investigated in developing rat brain. The contents of both the free and fatty-acylated forms of dolichol as well as the specific isoprenologues of dolichol were determined. Two distinctive phases of rapid dolichol deposition were observed; the first during brain development, and the second, with aging. The predominant form of brain dolichol was shown to be the free derivative at all ages; however, during the two phases of rapid deposition of total dolichol, fatty-acylated dolichol became detectable and increased transiently. The rapid rate of increase of brain dolichol during development occurred later than that of brain cholesterol, which shares a common biosynthetic pathway with dolichol. Thus, the peak rate of increase of dolichol occurred at 25 days postnatal, and of cholesterol, at 18 days postnatal. A distinct ontogenetic alteration in the proportion of the individual molecular species (isoprenologues) of dolichol also was defined. These observations suggest that dolichol is particularly involved in developmental events of the third to sixth postnatal weeks in rat brain, e.g. myelination and synaptogenesis.

The synthesis of a trisaccharide and a tetrasaccharide lipid intermediate. P1-dolichyl P2-[O-beta-D-mannopyranosyl-(1----4)-O-(2-acetamido-2-deoxy- beta-D-glucopyranosyl)-(1----4)-2-acetamido-2-deoxy-alpha-D- glucopyranosyl] diphosphate and P1-dolichyl P2-[O-alpha-D-mannopyranosyl-(1----3)-O-beta-D- mannopyranosyl-(1----4)-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)- (1----4)-2-acetamido-2-deoxy-alpha-D-glucopyranosyl] diphosphate

Synthetic benzyl O-(2,3,4,6,-tetra-O-acetyl-beta-D-mannopyranosyl)-(1-4)- (2-acetamido-3,6-di-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-(1-4)- 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside was converted, by catalytic hydrogenolysis of the benzyl groups, followed by treatment with acetyl chloride-hydrogen chloride and then "chloride-ion catalysis", into O-(2,3,4,6-tetra-O-acetyl- beta-D-mannopyranosyl)-(1-4)-O-(2-acetamido-3,6-di-O-acetyl-2-deoxy beta- D-glucopyranosyl)- (1-4)-2-methyl-(3,6-di-O-acetyl-1,2-dideoxy-alpha-D- glucopyrano)-[2,1-d]-2-oxazoline. This compound was phosphorylated by treatment with dibenzyl phosphate under strictly anhydrous conditions to give after catalytic hydrogenolysis, a peracetyl trisaccharide phosphate. This was coupled with P1-dolichyl P2-diphenyl diphosphate to give, after O-deacetylation, P1-dolichyl P2-[O- beta-D-mannopyranosyl- (1-4)-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)- (1-4)-2-acetamido-2-deoxy-alpha-D-glucopyranosyl] diphosphate, a trisaccharide "lipid intermediate". O-(2,3,4,6-Tetra-O-acetyl-alpha-D-mannopyranosyl)-(1-3)-O-(2,4,6-tri-O- acetyl-beta-D-mannopyranosyl)-(1-4)-O-(2-acetamido-3,6-di-O-acetyl-2- deoxy-beta- D-glucopyranosyl)- (1-4)-(2-acetamido-3,6-di-O-acetyl-2-deoxy-alpha-D-glucopyranosyl) phosphate, synthesized from O-alpha-D-mannopyranosyl-(1-3)-O-beta-D- mannopyranosyl-(1-4)-2-acetamido-2-deoxy-D-glucopyranose that had been isolated from mannosidosis urine was coupled with P1-dolichyl P2-diphenyl diphosphate to give, after O-deacetylation, P1-dolichyl P2-[O-alpha-D-mannopyranosyl- (1-3)-O-beta-D-mannopyranosyl-(1-4)-O-(2-acetamido-2-deoxy-beta-D- glucopyranosyl)-(1-4)-2-acetamido-2-deoxy-alpha-D-glucopyranosyl] diphosphate, a tetrasaccharide "lipid intermediate".

Induced mannosidosis-excretion of oligosaccharides by locoweed-intoxicated sheep

Daily urine samples were collected from a locoweed-fed sheep, and the oligosaccharide content examined by thin-layer and liquid chromatography. An unusual pattern of urine oligosaccharides was observed, which appears to be characteristic of loco intoxication. Changes in the pattern could be correlated with the onset of visible disease, which occurred approximately 5 weeks after the typical urine sugars were first detected. HPLC showed that these sugars consisted of two homologous series of oligosaccharides containing one and two residues of 2-acetamido-2-deoxy-D-glucose, respectively.

Solubilization of an alpha-(1 leads to 3)-D-mannosyltransferase from pancreas which utilizes synthetic dolichyl pyrophosphate trisaccharide beta-Man-(1 leads to 4)-beta-GlcNAc-(1 leads to 4)GlcNAc as substrate

Calf pancreas microsomes were treated with 0.5-1% Triton X-100 and the resulting soluble enzyme preparation was incubated with GDP-D-[14C]mannose. The addition of synthetic Dol-PP derivative of the trisaccharide beta-Man-(1 leads to 4)-beta-GlcNAc-(1 leads to 4)GlcNAc stimulated the synthesis of labeled lipid-bound tetrasaccharide 50-100-fold. The labeled tetrasaccharide thus formed was identified as alpha-Man-(1 leads to 3)-beta-Man-(1 leads to 4)-beta-GlcNAc- (1 leads to 4)GlcNAc by its chromatographic properties and by its sensitivity to alpha-mannosidase and to endo-beta-N-acetylglucosaminidase D. The solubilized alpha-(1 leads to 3)mannosyltransferase did not require divalent cation and was active in the presence of 10 mM EDTA.

Chromatographic separation of oligosaccharides from mannosidosis urine

A mixture of oligosaccharides was isolated from mannosidosis urine by a rapid and convenient procedure employing adsorption on activated charcoal. The mixture was partially fractionated into a homologous series of compounds by a rapid procedure employing a preparative, liquid chromatograph, and a more complete separation was obtained by a second chromatographic step employing a solid phase having more-powerful resolving properties, or by preparative-layer chromatography. The series of oligosaccharides was completely separated by 7-MPa, liquid chromatography (l.c.) on a Micropak NH2-10 column; the analysis could be performed with isocratic or gradient solvent-systems, and did not involve derivatization. With the isocratic system, a strict relationship was observed between retention time and the number of D-mannosyl residues. The use of 1,4-diaminobutane as a column "restorer" was evaluated.

Separation, quantitation and distribution of dolichol and dolichyl phosphate in rat and human tissues

Two procedures for quantitative determination of dolichol were studied and these were applied to analyze tissue and subcellular distribution. In the first procedure the dolichols were oxidized with Cr2O3 and reduced with NaB3H4. The radioactivity in the individual dolichols was measured using reversed-phase thin-layer chromatography. In the second procedure, dolichols were analyzed by high-pressure liquid chromatography. For determination of dolichyl phosphates the lipid extract was subjected to acid and alkaline hydrolysis, and after hydrolysis with acid phosphatase the distribution was determined by high-pressure liquid chromatography. Recovery was monitored by the addition of dolichol D15 and D23 phosphate to the homogenate. Rat spleen had the highest dolichol content (114 micrograms/g) followed by lower content in rat liver and brain. The distribution pattern was similar in all organs, with 18 and 19 isoprene residues as dominating components. Human organs contain considerably higher concentrations of dolichol, with the 19 and 20 isoprene residues as the main components. In rat liver, outer mitochondrial and Golgi membranes, lysosomes and plasma membranes contain considerable amounts of dolichol. A drastic increase in dolichol content was observed in rat liver hyperplastic nodules while human liver cirrhosis and hepatocarcinoma showed a marked decrease in dolichol. In the latter case, the distribution pattern was also changed. Of the total amount of dolichol present in the tissues, 2% was phosphorylated in human liver, 10% in human testis and 18% in rat liver. In rat liver mitochondria and in microsomes 4 and 31%, respectively, of the polyprenols were in activated form. The results demonstrated that dolichyl phosphate and dolichol concentrations were regulated by different mechanisms and that the two forms possessed an independent distribution.

High levels of brain dolichols in neuronal ceroid-lipofuscinosis and senescence

Dolichols as unesterified alcohols were identified as significant components of lipid extracts from storage cytosomes isolated post-mortem from the brains of patients with the infantile, late infantile, and juvenile types of neuronal ceroid-lipofuscinosis (NCL). Very small amounts of dolichols were present in the corresponding subcellular fractions of non-NCL brains. The nuclear fraction from NCL cerebral cortex contained the highest dolichol content expressed per milligram protein or lipid, whereas the crude mitochondrial fraction was the richest in normal brain. Highly significant elevations of dolichol levels were found in human cerebral cortex of patients with NCL and Alzheimer's disease compared with age-matched controls, but the levels were normal in Pick's disease. In human non-NCL cerebral cortex, dolichols increased from 16 micrograms/g at age 5 to over 200 at age 81. Rat cerebral cortex showed a similar progressive increase in dolichol content with age. The high dolichol values in NCL, Alzheimer's disease, and senescence appears to be related to the increase of lipofuscin in brain. This is the first time a uniform biochemical abnormality has been found in all childhood forms of NCL, but the enzyme defect is still unidentified. It may lie on pathways where dolichols and retinyl compounds are recycled in Golgi membranes and derived organelles during the biosynthesis of glycoproteins.

Novel mannose carrier in the trypanosomatid Crithidia fasciculata behaving as a short alpha-saturated polyprenyl phosphate

Crithidia fasciculata cells incubated with [14C]glucose or membranes derived from the same protozoan incubated with GDP-[14C]mannose were found to synthesize a lipid monophosphate mannose. No glucosylated mild acid-labile compound was formed in vivo or in vitro when UDP-[14C]glucose was used instead of GDP-[14C]mannose. The lipid moiety of the mannosyl derivative formed behaved as a polyprenol having 11 isoprene residues as judged by t.l.c. and be gel filtration in sodium deoxycholate-containing buffers. The mannolipid was not broken on treatment with hot phenol, suggesting the existence of an alpha-saturated isoprene unit. This is the first case reported in which a mannosyl phospholipid involved in sugar transfer in a eukaryotic cell behaves as if it was similar to that of bacterial polyprenols, although having its putative alpha-isoprene unit saturated to the same extent as dolichols from higher organisms.

Membrane fusion and glycosylation in the rat hepatic Golgi apparatus

When purified Golgi fractions were incubated with UDP-[3H]galactose in the absence of Triton-X-100, radioactivity was incorporated into an endogenous lipid and several peptide acceptors. Electron microscope analysis of Golgi fractions incubated in the endogenous galactosyl transferase assay medium revealed extensive fusion of Golgi saccules. Systematic removal of constituents in the galactosyl transferase assay medium showed enhanced (minus beta-mercaptoethanol) or reduced (minus ATP, minus sodium cacodylate buffer or minus MnCl2) fusion of Golgi membranes compared to the complete medium, Stereologic analysis revealed a correlation between membrane fusion and galactosyl transferase activity (r = 0.99, P less than 0.001). Electron microscope radioautography was carried out after incubation of Golgi fractions with UDP-[3H]galactose. Silver grains were not observed over trans elements of Golgi but were revealed mainly over large fused saccules with the number of silver grains being proportionate to membrane fusion (r = 0.92, P less than 0.001). Bilayer destabilization at points of Golgi membrane fusion may act to translocate galactose across the Golgi membrane and thereby provide a fusion regulated substrate for terminal glycosylation.

Synthesis of 2-methyl-[2-acetamido-4-O-acetyl-6-O-benzyl-3-O-(2-butenyl)-1,2-dideoxy-alpha-D -glucopyrano]-[2,1-d]-2-oxazoline, a versatile intermediate for the synthesis of complex oligosaccharides of bacterial cell-wall, human milk, and blood-group substances

2-Methyl-[2-acetamido-4-O-acetyl-6-O-benzyl-3-O-(2-butenyl)-1,2-dideoxy-alpha-D-glucopyrano]-[2,1-d]-2-oxazoline (2), a glycosylating agent in which the three hydroxyl groups are blocked with protecting groups of differing "persistence", is of utility in the synthesis of oligosaccharides containing highly branched 2-acetamido-2-deoxy-D-glucosyl residues, and it was synthesized in a ten-step sequence from 2-acetamido-2-deoxy-D-glucose via allyl 2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside (3). Alkylation of 3 with 2-butenyl (crotyl) bromide, hydrolysis of the benzylidene acetal group, benzylation of the 6-hydroxyl group, and acetylation of the 4-hydroxyl group afforded allyl 2-acetamido-4-O-acetyl-6-O-benzyl-3-O-(2-butenyl)-2-deoxy-beta-D-glucopyranoside(10). Treatment of 10 with chlorotris(tri-phenylphosphine)rhodium(I) gave mainly the corresponding 1-propenyl beta-glycoside, which was converted into oxazoline 2 by the action of mercuric chloride-mercuric oxide in acetonitrile. Glycosylation of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside with 2, and subsequent O-deacetylation at O-4' gave a glycosyl acceptor, benzyl 2-acetamido-4-O-[2-acetamido-6-O-benzyl-3-O-(2-butenyl) -2-deoxy-beta-D-glucopyranosyl]-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside .

The dependence of glycosyltransferases in Dictyostelium discoideum on the structure of polyisoprenols

Mannosyltransferases in plasma membranes of Dictyostelium discoideum synthesize polyisoprenylphosphomannosides from exogenous polyisoprenylphosphates and GDP-mannose. The specificity of the enzymes depends on the chain length and the saturation of the polyisoprenols. Maximum activity is reached by a alpha-saturated C-55 polyisoprenylphosphate.

Enzymatic glucosylation of dolichyl monophosphate formed via cytidine triphosphate in calf brain membranes

When calf brain membrane preparations containing endogenous dolichyl [32P]monophosphate (Dol-32P), prelabeled enzymatically by [gamma-32P]-CTP, are incubated with unlabeled UDP-glucose, the formation of a mild acid-labile [32P]phosphoglucolipid is observed. The biosynthesis of the [32P]phosphoglucolipid is dependent on the concentration of UDP-glucose added, and no [32P]phosphoglycolipid appeared when UDP-glucose was replaced by ADP-glucose, UDP-xylose, UDP-galactose, UDP-mannose, or UDP-glucuronic acid. The 32P-labeled product formed by the UDP-glucose-dependent reaction is chemically and chromatographically identical to glucosylphosphoryldolichol. Several enzymatic parameters of the glucosylation of the specific pool of Dol-P, synthesized by the CTP-mediated kinase, and the total available pool of Dol-P have been compared by a double-label assay utilizing endogenous, prelabeled Dol-32P and UDP-[3H]glucose as substrates.

Partial characterization of the polyisoprenoid carrier of N-acetylglucosamine in Glycine max (soya bean)

Dolichyl phosphate (C55) and dolichyl phosphate prepared from liver were incubated with an enzyme prepared from soya-bean protoplasts. They both stimulated the transfer of radioactivity from UDP-D-glucose to lipid, but the stimulation was greater with liver dolichyl phosphate. Liver dolichyl phosphate with the soya-bean enzyme stimulated the transfer of radioactivity from UDP-N-acetyl-D-[U-14C]glucosamine to acidic lipid. UDP-D-[U-14C]glucose and UDP-N-acetyl-D-[U-14C]glucosamine were used with the soya-bean enzyme to prepare the glycosylated-acid-lipid acceptor of each sugar. Mild acid hydrolysis revealed that the radioactivity in the lipid glucosylated from UDP-glucose was present exclusively as glucose. That in the lipid glycosylated from UDP-N-acetylglucosamine was present mostly as N-acetylglucosamine. The soya-bean acidic-lipid acceptors of glucose and N-acetylglucosamine were stable to both catalytic hydrogenation and treatment with hot aqueous phenol; they behaved in a similar way as authentic alpha-saturated glucosylated polyisoprenyl phosphates. The soya-bean acidic-lipid acceptors of glucose and N-acetylglucosamine were eluted as deoxycholate complexes from a Sephadex column. In comparison with glucosylated polyisoprenyl phosphates of known size, the patterns of elution indicated that both soya-bean lipids contained a polyisoprenoid chain of 18 isoprene units.

The presence of dolichol in a lipid diphosphate N-acetylglucosamine from Saccharomyces cerevisiae (baker's yeast)

The lipid moiety of a lipid diphosphate N-acetylglucosamine, an intermediate in glycosylation of proteins, was studied. Ozonolysis of the compound gave evidence for an alpha-saturated isoprene unit. Alkaline hydrolysis of the glycolipid, followed by high-pressure liquid chromatography, showed the presence of a series of polyprenol homologues identical with those isolated directly from Saccharomyces cerevisiae (baker's yeast). No particular homologue was preferred in the enzymic transfer of N-acetylglucosamine 1-phosphate to endogenous dolichol monophosphate.

Microdetermination of dolichol in tissues

A method is described for the rapid purification and analysis of tissue dolichol on a nanomole scale. The assay is based on a radioisotope dilution technique in which [3H]dolichyl palmitate is used as tracer and acetylation with [14C]acetic anhydride serves as the quantitating reaction. The acetylation conditions were characterized with respect to time, temperature and concentration of reagents. When this method was applied to pig liver, a value was obtained which fell within the range of previously published results based on a gravimetric assay. In chicken, dolichol levels were found to be high in oviduct and low or absent in red blood cells and plasma.

The high-performance liquid-chromatographic analysis of ficaprenol and dolichol

A high-performance liquid-chromatographic method was devised which is capable of resolving the p-nitrobenzoyl derivatives of polyprenols containing 35-110 or more carbon atoms. This procedure was used for the determination of ficaprenol and pig liver dolichol composition and can be applied to mixtures of polyprenols as an analytical or preparative technique.

Incorporation of mannose and glucose into prenylphosphate sugars in isolated human platelet membranes

Isolated platelet membranes synthesize mannosylretinyl phosphate and dolichylmannosyl phosphate from GDP-[14C]mannose, but only dolichylglucosyl-phosphate is synthesized from UDP-[14C]glucose. Addition of exogenous retinylphosphate specifically stimulates the biosynthesis of mannosylretinylphosphate.

A lipid linked oligosaccharide which contains hexosamine, mannose and glucose

Previous work showed that liver microsomes catalyze the transfer of glucose from dolichol monophosphate glucose to an endogenous acceptor believed to be a dolichol pyrophosphate derivative of an oligosaccharide. This oligosaccharide has now been prepared on a larger scale so as to permit the determination of its sugars. The purification procedure includes, as a last step, a thin layer chromatography on kieselguhr-silica gel to obviate glucose-containing contaminants. After complete hydrolysis mannose, glucose and a small amount of hexosamine were detected.

Synthesis of polyprenol-monophosphate- beta -galactose by acetobacter xylinum

A particulate enzyme preparation from Acetobacter xylinum synthesizes ficaprenol-monophosphate-beta-galactose from ficaprenol monophosphate (FMP) and UDP-galactose in the presence of detergent. The product has the same properties as those previously reported for the compound formed with the endogenous acceptor. Dolichol-monophosphate (DolMP) is also a good galactose acceptor but the product obtained has different properties. Lipid extracts from Acetobacter contain galactose acceptor capacity which is lost by mild acid treatment. FMP behaves in a similar manner but DolMP is resistant to this treatment. It is concluded that the endogeneous acceptor is an allylic phosphate ester of a polyprenol.