Sterols function

W. Koller, Antifungal Agents with Target Sites in Sterol Function and Biosynthesis , in Target Sites of Fungicide Action , ed. W. Koller, CRC Press, Boca Raton, FL, 1992, pp. 119-206. 

XIII) The conversion of lanosterol to cholesterol (I) Sterol function... 

A similar mechanism for the formation of alkyl sterols functions in Euglena and the Xanthophyte Monodus subterraneus. 

Koller W. Antifungal agents with target sites in sterol functions and biosynthesis. In Killer W, ed. Target Sites of Fungicide Action. Boca Raton, FL CRC Press, 1992 119-206. 

With certain Oomycetes, "sterol-like molecules, eg. tetracyclic and pentacyclic triterpenoids (Fig. 2), may produce the same physiological end response as sterols (2). The growth response to these polycyclic isopentenoids is intimately associated with their 3-dimen-sional geometry, molecular features and subcellular quantity. In order to discuss sterol function for What we assume is an evolutionary determinant of developmental change, a brief overview of sterol occurrence and biosynthesis is given first. 

This trace sterol may also permit other conq>ounds, eg. cycloartenol (6.31). to act in a synergistic or sparking (32) capacity allowing for growth stimulation and oogonia induction (cf. Sterol Function Section). Concerning the cholesterol identified in other Oomycetes... 

Briill F, Mensink RP, Plat J (2009) Plant sterols functional lipids in immune function and inflammation Future Lipidology 4(3) 355-365. doi 10.2217/CLP.09.26... 

Sterol function Required media concentration of sterol Definition... 

In milk fat, cholesterol is associated with Hpoproteins in the milk fat globule. It is also a component of animal membranes and controls rigidity and permeabihty of the membranes. Cholesterol has interesting surface properties and can occur in Hquid crystalline forms. Plants contain sterols such as P-sitosterol [83-46-5] (4b) or stigmasterol [83-48-7] (4c). Their functions in plant metaboHsm are not yet well understood. Analysis of sterols has proven useful for detection of adulteration of edible fats (9). 

Antioxidants (qv) have a positive effect on oils when present in the proper concentration. Sterols and tocopherols, which are natural antioxidants, may be analy2ed by gas-Hquid chromatography (glc), high performance Hquid chromatography (hplc), or thin-layer chromatography (tic). Synthetic antioxidants maybe added by processors to improve the performance or shelf life of products. These compounds include butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), / fZ-butyUiydroquinone (TBHQ), and propyl gallate. These materials may likewise be analy2ed by glc, hplc, or tic. Citric acid (qv), which functions as a metal chelator, may also be deterrnined by glc. 

In general, the sterols perform a structural function, for example as components of the lipid layers of membranes. The Cis, C19 and C21 steroids mainly perform an endocrine function. In other words they are hormones. The bile salts (C24-steroids) fulfil a functional role in digestion in animals. 

Many examples of microbial hydroxylation of sterols/steroids have been reported. These hydroxylations usually involve mixed function oxidases which utilise molecular oxygen and cytochrome P-450. The reaction can be represented by ... 

CYP27A1 catalyzes the side chain oxidation (27-hydroxylation) in bile acid biosynthesis. Because bile acid synthesis is the only elimination pathway for cholesterol, mutations in the CYP27A1 gene lead to abnormal deposition of cholesterol and cholestanol in various tissues. This sterol storage disorder is known as cerebrotendinous xanthomatosis. CYP27B1 is the 1-alpha hydroxylase of vitamin D3 that converts it to the active vitamin form. The function of CYP27C1 is not yet known. 

In addition to the described lipid pathways mainly operative in macrophages, two further ABC-transporteis, ABCG5 and ABCG8 have been implicated in the efflux of dietary sterols from intestinal cells back into the gut lumen and from liver to the bile duct (Fig 1). Both ABC-transporters form a functional heterodimer with highest expression levels in liver and intestine and are regulated... 

Although no drugs directly targeting the sterol transporters described above are available, the function of several lipid lowering diugs is associated with interaction with ABCA1. 

The sterols and sterolins in rice bran are potent immunomodulators. The best response was obtained with a 100 1 sterol/sterolin mixture that demonstrated T-cell proliferation from 20% to 920% and active cell antigens after four weeks in human subjects (Bouic et al, 1996). Another in vitro experimental study with sterol/sterolins, demonstrated a significant increase in cytokinines, interleukin-2 and y-interferon between 17% and 41 % in addition to an increase in natural killer cell activity. These experiments (Bouic et al, 1996) prove that sterol/sterolins are potent immunomodulators with important implications for the treatment of immune dysfunction. Rice bran products are excellent dietary supplements for the improvement of immune function. It is probable that the effects of rice bran on diabetes, CVD and cancer all result from improved immune function. 

Piironen V et al (2000) Plant sterols biosynthesis, biological function and their importance to human nutrition. J Sci Food Agric 80(7) 939—966... 

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