Sterol

About: Sterol is a research topic. Over the lifetime, 8117 publications have been published within this topic receiving 309926 citations. The topic is also known as: sterols & sterol lipids.

Plant sterols: Diversity, biosynthesis, and physiological functions

Abstract: Sterols, which are isoprenoid derivatives, are structural components of biological membranes. Special attention is now being given not only to their structure and function, but also to their regulatory roles in plants. Plant sterols have diverse composition; they exist as free sterols, sterol esters with higher fatty acids, sterol glycosides, and acylsterol glycosides, which are absent in animal cells. This diversity of types of phytosterols determines a wide spectrum of functions they play in plant life. Sterols are precursors of a group of plant hormones, the brassinosteroids, which regulate plant growth and development. Furthermore, sterols participate in transmembrane signal transduction by forming lipid microdomains. The predominant sterols in plants are β-sitosterol, campesterol, and stigmasterol. These sterols differ in the presence of a methyl or an ethyl group in the side chain at the 24th carbon atom and are named methylsterols or ethylsterols, respectively. The balance between 24-methylsterols and 24-ethylsterols is specific for individual plant species. The present review focuses on the key stages of plant sterol biosynthesis that determine the ratios between the different types of sterols, and the crosstalk between the sterol and sphingolipid pathways. The main enzymes involved in plant sterol biosynthesis are 3-hydroxy-3-methylglutaryl-CoA reductase, C24-sterol methyltransferase, and C22-sterol desaturase. These enzymes are responsible for maintaining the optimal balance between sterols. Regulation of the ratios between the different types of sterols and sterols/sphingolipids can be of crucial importance in the responses of plants to stresses.

Structure and Function of Sterols in Fungi

Abstract: Publisher Summary This chapter discusses the structure and function of sterols in fungi. The distribution of sterols among fungi follows the taxonomic separation of fungi at the subdivision level. The Mastigomycotina, or lower fungi, produce mainly cholesterol and/or its C-24 alkyl and/or alkylidene derivatives, but no ergosterol. There is less distinction among fungi at the class level with respect to sterol composition among the Mastigomycotina. Fucosterol is a major sterol of many sterol-producing Oomycetes and may be accompanied by cholesterol and 24-methylene cholesterol. Cholesterol is produced by some but not all Chytridiomycetes, which, along with the Hypochytriomycetes, have 24-alkyl rather than 24-alkylidene derivatives as major sterols. It is well-known that the pythiaceous fungi (Oomycetes) do not produce sterols because they cannot carry out the epoxidation of squalene, and it is believed that Plasmodiophoromycetes, which are obligate parasites, also do not produce sterols. Sterols are synthesized by enzymes located mainly in the endoplasmic reticulum, but they do not tend to accumulate there or in endomembranes derived from the endoplasmic reticulum.