Cytotoxic and Membrane Cholesterol Effects of Ultraviolet Irradiation and Zinc Oxide Nanoparticles on Chinese Hamster Ovary Cells.

Zinc Oxide (ZnO) nanoparticles are suspected to produce toxic effects toward mammalian cells; however, discrepancies in the extent of this effect have been reported between different cell lines. Simultaneously, high levels of ultraviolet (UV-C) radiation can have carcinogenic effects. The mechanism of this effect is also not well understood.

Purification, characterization and inhibition of sterol C24-methyltransferase from Candida albicans.

Solubilized sterol C24-methyltransferase (24-SMT) was purified to homogeneity from a cell extract of the yeast Candida albicans (Ca) by anion exchange chromatography, gel permeation chromatography and fast performance liquid chromatography using a Mono Q column. The purified enzyme has an apparent molecular mass of 178 kDa on gel permeation chromatography and 43 kDa on SDS/PAGE, indicating that it is composed of four identical subunits. The substrate requirement of the native enzyme has an optimal specificity for zymosterol with associated kinetic constants of K(m) 50 μM and k(cat) of 0.

Cloning, mechanistic and functional analysis of a fungal sterol C24-methyltransferase implicated in brassicasterol biosynthesis.

The first committed step in the formation of 24-alkylsterols in the ascomycetous fungus Paracoccidiodes brasiliensis (Pb) has been shown to involve C24-methylation of lanosterol to eburicol (24(28)-methylene-24,25-dihydro-lanosterol) on the basis of metabolite co-occurrence. A similarity-based cloning strategy was employed to obtain the cDNA clone corresponding to the sterol C24-methyltransferase (SMT) implicated in the C24-methylation reaction. The resulting catalyst, prepared as a recombinant fusion protein (His/Trx/S), was expressed in Escherichia coli BL21(C43) and shown to possess a substrate specificity for lanosterol and to generate a single exocyclic methylene product.

Disruption of ergosterol biosynthesis, growth, and the morphological transition in Candida albicans by sterol methyltransferase inhibitors containing sulfur at C-25 in the sterol side chain.

The sterol substrate analog 25-thialanosterol and its corresponding sulfonium salt were evaluated for their ability to serve as antifungal agents and to inhibit sterol methyltransferase (SMT) activity in Candida albicans. Both compounds inhibited cell proliferation, were fungistatic, interrupted the yeast-like-form to germ-tube-form transition, and resulted in the accumulation of zymosterol and related delta24-sterols concurrent with a decrease in ergosterol, as was expected for the specific inhibition of SMT activity. Feedback on sterol synthesis was evidenced by elevated levels of cellular sterols in treated vs.

Evidence for multiple sterol methyl transferase pathways in Pneumocystis carinii.

The sterol composition of Pneumocystis carinii, an opportunistic pathogen responsible for life-threatening pneumonia in immunocompromised patients, was determined. Our purpose was to identify pathway-specific enzymes to impair using sterol biosynthesis inhibitors. Prior to this study, cholesterol 15 (ca.