title: The stereochemistry of hexahydroprenol, ubiquinone and ergosterol biosynthesis in the mycelium of Aspergillus fumigatus Fresenius.
abstract: 1. The mycelium of Aspergillus fumigatus has been shown to incorporate mevalonate into squalene, ubiquinone, ergosterol and hexahydroprenol. 2. The (3)H/(14)C ratio in ubiquinone, biosynthesized from [2-(14)C-(4R)-4-(3)H(1)]mevalonate, is the same as in the squalene; essentially no (3)H was incorporated from [2-(14)C-(4S)-4-(3)H(1)]mevalonate, indicating the biosynthesis of biogenetically trans-isoprene units. 3. The (3)H/(14)C ratio for ergosterol (from ;4R-mevalonate') was 3:5, showing that the proton at C-24 is not lost during alkylation of the side chain; it probably migrates to C-25. 4. As (3)H from both mevalonates was incorporated into the hexahydroprenols the biosynthesis of both cis- and trans-isoprene units must occur. 5. The saturated omega- and psi-isoprene units are shown to be biogenetically trans, as are two of the unsaturated residues. 6. The saturated alpha- and unsaturated beta-isoprene residues are both biogenetically cis. 7. An inexplicable loss of approximately half of the olefinic protons from the cis-portion of hexahydroprenol occurs; possible reasons for this loss are discussed. 8. Increase in chain length of the hexahydroprenols is by a cis addition. 9. A biosynthesis of hexahydroprenols by addition of cis-isoprene units to all-trans-geranylgeranyl pyrophosphate, or a dihydro or tetrahydro derivative thereof, is suggested.
mesh_terms: D000438:Alcohols / Q000096:biosynthesis*; D001230:Aspergillus / Q000378:metabolism*; D002247:Carbon Isotopes; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D011756:Diphosphates / Q000378:metabolism; D008798:Mevalonic Acid / Q000378:metabolism*; D010126:Ozone; D013185:Squalene / Q000096:biosynthesis*; D014316:Tritium; D014451:Ubiquinone / Q000096:biosynthesis*; D014807:Vitamin D / Q000096:biosynthesis*
chemical_list: D000438:Alcohols; D002247:Carbon Isotopes; D011756:Diphosphates; D014316:Tritium; D014451:Ubiquinone; D014807:Vitamin D; D010126:Ozone; D013185:Squalene; D008798:Mevalonic Acid