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

Dolichol biosynthesis: the occurrence of epoxy dolichol in skipjack tuna liver

Polyisoprenoid alcohols from the livers of temperate sea fish (skipjack tuna, chub mackerel, red sea bream and rainbow trout) were analyzed by using 2D-TLC, electrospray ionization (ESI) mass spectrometry and NMR methods. Dolichols (Dols) were detected in all the fish livers, and they were composed of 19-22 isoprene units with Dol-20 as the predominant prenolog. In addition, Dol-like family compounds were found by using 2D-TLC on skipjack tuna samples. These compounds were found to have a larger molecular mass than the Dol family by 16 mass units. NMR analysis indicated that the Dol-like compounds were consistent with the terminal epoxide structure of Dols (the ω-oxirane derivatives of Dols). ESI analysis also revealed the occurrence of dehydro molecules in both Dols and epoxy Dols (Dol-like) fractions. The occurrence of epoxy Dols in fish is discussed in context with the biosynthesis of Dols, which is responsible for forming Dol phosphate, which lead to Dol-PP-oligosaccharide.

HPLC and mass spectrometry analysis of dolichol-phosphates at the cell culture scale

Dolichols (Dol) are polyprenol lipids that are essential structural components of eukaryotic membranes. In addition, the phosphorylated derivatives of Dol function as lipid anchors of mono- and oligosaccharide precursors involved in protein glycosylation. The biological importance of Dol phosphates (Dol-P) is illustrated by the severe outcome of human disorders linked to Dol biosynthetic defects, such as Dol-kinase deficiency. For characterization of inherited human diseases and evaluation of therapeutic trials, cultured cells often serve as a sole possible source for experimentation. Limited amounts of cell culture material render the quantitative analysis of Dol a challenging task. Here, we present HPLC- and mass spectrometry-based approaches to analyze and quantitate Dol-P from cultured human cells. The composition of naturally occurring Dol-P and the saturation state of the alpha-isoprene units was identified by negative-ion electrospray ionization mass spectrometry. Furthermore, fluorescently labeled Dol-P were separated by HPLC and quantified by comparison to known amounts of the internal standard polyprenol-P. The effect of pravastatin, a 3-hydroxy-3-methyl-glutaryl coenzyme-A reductase inhibitor, on the formation of Dol-P in HeLa cells was investigated. As expected, this treatment led to a decrease of Dol-P down to 35% of normal levels.