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

Separation and quantitative determination of dolichol and dolichyl phosphate in rat and trout liver

The dolichol concentrations in rat and trout liver were found respectively to be 50-59 and 16-21 micrograms/g using three experimental methods: densitometric scanning of thin-layer plates, colorimetric assay and HPLC analysis. By HPLC of benzoylated dolichols, the distribution of the dolichols according to the number of their isoprene residues, was determined in rat and trout liver. The major component was dolichol -18 in rat and dolichol -19 in trout liver. Dolichyl phosphate concentrations were found to be 6-7 micrograms/g of rat liver and 8-9 micrograms/g of trout liver by densitometric scanning of thin-layer plates.

High-performance liquid chromatographic method for the determination of dolichols in tissues and plasma

High-performance liquid chromatographic methods for the determination of dolichols in tissues and plasma have been developed. The tissue concentration of dolichols was measured by high-performance liquid chromatography with uv detection and plasma levels of dolichols were determined fluorometrically after derivatization with anthracene-9-carboxylic acid. In both methods, 2,2-didecaprenylethanol was used as an internal standard. The method with fluorescence detection was sufficiently sensitive to measure the concentration of dolichols in human plasma.

Distribution, metabolism and function of dolichol and polyprenols

Polyisoprenoid alcohols consisting of 9 or more isoprene units are present in all living cells. They can be fully unsaturated (polyprenols) or alpha-saturated (dolichol). Dolichol forms may have additional saturation at or near the omega-end. Some species contain ony dolichol or only polyprenols while others have nearly equal amounts of both types. Some polyisoprenoid alcohols consist entirely of trans isoprene units but most, including dolichol, contain both trans and cis units. Considerable advances in lipid methodology have occurred since the first review of polyisoprenoid alcohols by Hemming in 1974. For example, direct analysis of both dolichol and Dol-P by HPLC has replaced earlier methods which were often both insensitive and inaccurate. The availability of radiolabeled dolichol and polyprenols has facilitated studies concerning the metabolism and distribution of these compounds. Those studies suggest that only a small portion of the dolichol present in cells is likely to be involved in glycosylation. Polyisoprenoid alcohols are usually present at a family of homologues where each differs in size by one isoprene unit. Little or no size related specificity has been observed for any reaction involving dolichol or polyisoprenol intermediates. The overall length of polyisoprenoid alcohols may, however, affect the manner in which these compounds influence the physical and biochemical properties of membranes. Studies on the biosynthetic pathway leading from cis, trans Pol-PP by phosphatase action. The formation of the dolichol backbone from a polyprenol requires the action of an additional enzyme, an alpha-saturase. This enzyme does not always act at the level of a single common substrate, since Pol-PP, Pol-P, and polyprenol all appear to be utilized as substrates. The major product of the de novo pathway differs among different species. Dol-P would appear to be the most energy efficient end-product since it can participate directly in glycoprotein formation. Most often, however, Dol-P is not the major product of metabolic labeling experiments. In some cases, dolichol is formed so that rephosphorylation is required to provide Dol-P for participation in glycoprotein formation. The kinase responsible for this phosphorylation appears to bypass the considerable stores of dolichol present in tissues (i.e. sea urchin eggs) in favor of dolichol derived directly from de novo synthesis. Although HMGR is a major regulatory component of the pathway leading to polyisoprenoid alcohols and cholesterol, control is most often not co-ordinated.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Analysis of dolichol in human tissues by high pressure liquid chromatography

Dolichol from human liver was shown by reverse-phase high pressure liquid chromatography to consist of a series of homologues ranging in length from 17 to 23 isoprene units. The two major components, corresponding to 19 and 20 isoprene units, respectively, were isolated and identified by mass spectrometry. Dolichyl palmitate, synthesized from liver dolichol, showed an identical series of peaks with longer retention times. Attempts to chromatography dolichyl phosphate under similar conditions were unsuccessful. Dolichol from uterine tissue and several other human tissues showed a shift toward shorter chain length, with a predominance of homologues containing 18 and 19 isoprene units.

A dolichyl phosphate-cleaving acid phosphatase from Tetrahymena pyriformis

Tetrahymena pyriformis contains an enzyme which hydrolyzed dolichyl phosphate. This activity was solubilized from lyophilized samples of this organism and was relatively stable when stored frozen. The soluble enzyme preparation had an acid pH optimum and hydrolyzed both dolichyl and phytanyl phosphates at equivalent rates. The polyprenylphosphate phosphatase activity was compared with the acid phosphatases which hydrolyzed p-nitrophenyl phosphate and marked differences were found. Dolichyl phosphate hydrolysis required Mg2+ for maximum activity while the bulk of the phosphatase activity was not effected by the absence of this ion. Other differences were that the polyprenylphosphate phosphatase was relatively insensitive to inhibitors such as tartrate and vanadium oxide sulfate which had a pronounced effect on the rate of p-nitrophenyl phosphate hydrolysis. The two activities also appeared to have different subcellular distributions. The polyprenylphosphate phosphatase was markedly inhibited by ethoxy formic anhydride, a reagent which is active against enzymes containing a histidine residue at their active site, while p-nitrophenyl phosphate hydrolysis was unaffected. The polyprenylphosphate phosphatase may be important in regulating the level of dolichyl phosphate in T. pyriformis and thus the rate of glycoprotein synthesis. It is also a useful tool which is capable of liberating dolichol from dolichyl phosphate under mild conditions which will permit the further characterization of the polyprenols.