Concerning the role of 24,25-dihydrolanosterol and lanostanol in sterol biosynthesis by cultured cells.
Rat hepatoma cells (H4-II-E-C3) efficiently converted a dietary supplement of [2-3H]24,25-dihydrolanosterol (1) to [3H]cholesterol while [2-3H]lanostanol (4,4,14 alpha-trimethylcholestanol (2) was recovered from the cells without apparent transformation, although it was esterified and induced an accumulation of lanosterol. A comparison of the chromatographic (TLC, GLC and HPLC), spectral (MS and 1H-NMR) and physical properties of 1 and 2 is given for the first time. The inability to detect 2 in nature coupled with our findings that 1 but not 2 is metabolized to cholesterol by H4 cells is interpreted to imply that the biosynthetic inclusion of the delta 8(9)-bond during the cyclization process of squalene-oxide to a tetracyclic product is an evolutionary adaptation selected for because the olefinic linkage is structually important in the subsequent conversion of lanosterol and its stereoisomers, e.g., cycloartenol, to delta 5-sterols.
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Plant Physiology Research Unit, Russell Research Center, USDA, Athens, GA 30613.
Norton
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RA
Parish
E J
EJ
Meenan
A
A
Popják
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G
D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D008401:Gas Chromatography-Mass Spectrometry; D007810:Lanosterol / Q000031:analogs & derivatives* / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D051381:Rats; D013261:Sterols / Q000378:metabolism*; D014316:Tritium; D014407:Tumor Cells, Cultured
D013261:Sterols; D014316:Tritium; D007810:Lanosterol; C015316:lanostenol