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#sterol

2 public questions tagged with this topic.

Glycolipid and Phospholipid

Which sterol is abundant in plant membranes?

Plant membranes replace cholesterol phytosterols where stigmasterol and sitosterol are prominent structurally related functionally overlapping but distinct regulation. Both derive cycloartenol via CYP51 SMT1 SMT2 sterol methyltransferases, with sitosterol bearing twenty four alpha ethyl group dominating sixty percent free sterols stigmasterol bearing additional trans double bond C22 C23 introduced CYP710A comprising ten to thirty percent campesterol ten percent remainder. In most crops soybean Arabidopsis tomato sitosterol quantitative major but stigmasterol characteristic marker plasma membranes detergent resistant rafts showing inducible increase pathogen challenge avirulent bacteria senescence mediated PLD phospholipase D signaling and ROS tolerance membrane remodelling. Cholesterol minor less than five percent, ergosterol dominates fungi mycobacteria. Phytosterols regulate membrane order permeability ion channels H ATPase activity auxin transport PIN localization brassinosteroid precursor campesterol growth regulation. Ratio sitosterol stigmasterol modulates fluidity freezing tolerance via CBF pathway COR genes. Understanding phytosterol diversity illustrates evolutionary adaptation where cholesterol function fulfilled ethyl sterols explaining dietary plant sterol interference human cholesterol absorption via Niemann Pick C1 Like one transporter NPC1L1 competitor heart health and plant physiology cold adaptation topics in exams.

Ref: Schaller H., Plant Physiol 2003, Plant sterols stigmasterol sitosterol biosynthesis and membrane functions.

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Glycolipid and Phospholipid

Which sterol is found predominantly in fungal membranes?

Fungal membrane physiology diverges animal via ergosterol predominance conferring distinct drug susceptibility exploitable therapeutically antifungal agents. Ergosterol contains conjugated double bonds C5-C6 C7-C8 B ring C22-C23 side chain plus methyl C24 introduced ERG6 methyltransferase producing more bent shape than cholesterol increasing membrane condensing effect. Biosynthesis squalene lanosterol involves ERG11 C14 demethylase cytochrome P450 targeted fluconazole itraconazole voriconazole isavuconazole, ERG3 ERG5 desaturases ERG4 reductase. Ergosterol optimizes membrane proteins Pma1 proton pump Pdr efflux pumps regulates fluidity acidic pH hyphal growth dimorphism. Human membranes cholesterol lacking these features so polyenes amphotericin B nystatin bind ergosterol eight fold stronger forming extramembranous sponge extracting sterol creating zero point eight nanometer pores causing potassium leakage oxidative death via reactive oxygen. Stigmasterol sitosterol dominate plants phytosterols. Understanding ergosterol uniqueness explains fungicidal mechanisms resistance via ERG3 mutation shunting to fourteen alpha methylfecosterol less toxic, evolution membrane sterols, core microbiology medical mycology topic essential pharmacology antifungal stewardship and cell biology exams differentiating sterol types among kingdoms and therapeutic windows.

Ref: Rodrigues ML, mBio 2018, Ergosterol in fungal membranes and antifungal targeting strategies.

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