8 research outputs found
Dolichol: A Component of the Cellular Antioxidant Machinery
Dolichol, an end product of the mevalonate pathway, has been proposed a biomarker of aging, but its biological role, not to mention its catabolism, has not been fully understood. UV-B radiation was used to induce oxidative stress in isolated rat hepatocytes by the collagenase method. Effects on dolichol, phospholipids-bound polyunsaturated fatty acids (PL PUFA) and known lipid soluble antioxidants [coenzyme Q (CoQ) and α-tocopherol] were studied. The increase in oxidative stress was detected by a probe sensitive to reactive oxygen species (ROS). Peroxidation of lipids was assessed by measuring the release of thiobarbituric acid reactive substances (TBARS). Dolichol, CoQ and α-tocopherol were assessed by high-pressure liquid chromatography (HPLC), PL PUFA by gas-liquid chromatography (GC). UV-B radiation caused an immediate increase in ROS as well as lipid peroxidation and a simultaneous decrease in the levels of dolichol and lipid soluble antioxidants. Decrease in dolichol paralleled changes in CoQ levels and was smaller than that in α-tocopherol. The addition of mevinolin, a competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoAR), magnified the loss of dolichol and was associated with an increase in TBARS production. Changes in PL PUFA were minor. These findings highlight that oxidative stress has very early and similar effects on dolichol and lipid soluble antioxidants. Lower levels of dolichol are associated with enhanced peroxidation of lipids, which suggest that dolichol may have a protective role in the antioxidant machinery of cell membranes and perhaps be a key to understanding some adverse effects of statin therapy
Antibacterial, cytotoxic and genotoxic activity of nitrogenated and haloid derivatives of C50–C60 and C70–C120 polyprenol homologs
Analysis of plant polyisoprenoids
Polyisoprenoid alcohols are representatives of high-molecular terpenoids. Their hydrocarbon chains are
built of 5 to more than 100 isoprene units giving rise to polymer molecules that differ in chain-length
and/or geometrical configuration. Plants have been shown to accumulate diverse polyisoprenoid mixtures
with tissue-specific composition. In this chapter, methods of analysis of polyisoprenoid alcohols in plant
material are described, including isolation and purification of polyisoprenoids from plant tissue, fast semiquantitative analysis of the polyisoprenoid profile by thin-layer chromatography (straight phase adsorption and reversed phase partition techniques), and quantification of polyisoprenoids with the aid of high performance liquid chromatography. This approach results in full characterization of complex polyisoprenoid mixtures accumulated in various plant tissues and other matrixes
The C-terminal domain of the Salmonella enterica WbaP (UDP-galactose:Und-P galactose-1-phosphate transferase) is sufficient for catalytic activity and specificity for undecaprenyl monophosphate
Two families of membrane enzymes catalyze the initiation of
the synthesis of O-antigen lipopolysaccharide. The
Salmonella enterica Typhimurium WbaP is a prototypic
member of one of these families. We report here the purification
and biochemical characterization of the WbaP
C-terminal (WbaPCT) domain harboring one putative
transmembrane helix and a large cytoplasmic tail. An Nterminal
thioredoxin fusion greatly improved solubility and
stability of WbaPCT allowing us to obtain highly purified
protein. We demonstrate that WbaPCT is sufficient to catalyze
the in vitro transfer of galactose (Gal)-1-phosphate from
uridine monophosphate (UDP)-Gal to the lipid carrier undecaprenyl
monophosphate (Und-P). We optimized the in vitro
assay to determine steady-state kinetic parameters with the
substrates UDP-Gal and Und-P. Using various purified polyisoprenyl
phosphates of increasing length and variable saturation
of the isoprene units, we also demonstrate that the
purified enzyme functions highly efficiently with Und-P,
suggesting that theWbaPCT domain contains all the essential
motifs to catalyze the synthesis of the Und-P-P-Gal molecule
that primes the biosynthesis of bacterial surface glycans
Double Bond Stereochemistry Influences the Susceptibility of Short‑Chain Isoprenoids and Polyprenols to Decomposition by Thermo‑Oxidation
Alcohols are common constituents of
living cells. They are usually assigned a role in the adaptation
of the cell to environmental stimuli, and this process
might give rise to their oxidation by reactive oxygen
species. Moreover, cellular isoprenoids may also undergo
various chemical modifications resulting from the physicochemical
treatment of the tissues, e.g., heating during food
processing. Susceptibility of isoprenoid alcohols to heat
treatment has not been studied in detail so far. In this study,
isoprenoid alcohols differing in the number of isoprene units
and geometry of the double bonds, β-citronellol, geraniol,
nerol, farnesol, solanesol and Pren-9, were subjected to
thermo-oxidation at 80 °C. Thermo-oxidation resulted in the
decomposition of the tested short-chain isoprenoids as well
as medium-chain polyprenols with simultaneous formation
of oxidized derivatives, such as hydroperoxides, monoepoxides,diepoxides and aldehydes, and possible formation of oligomeric derivatives. Oxidation products were monitored by GC-FID, GC-MS, ESI-MS and spectrophotometric methods. Interestingly, nerol, a short-chain isoprenoid with a double bond in the cis (Z) configuration, was more oxidatively stable than its trans (E) isomer, geraniol. However, the opposite effect was observed for medium-chain polyprenols, since Pren-9 (di-trans-poly-cis-prenol) was more susceptible to thermo-oxidation than its all-trans isomer, solanesol. Taken together, these results experimentally confirm that both short- and long-chain polyisoprenoid alcohols are prone to thermo-oxidation