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A polyprenol complex of Aspergillus niger was shown, by using spectrometric methods, to consist of a family of exo-methylene-hexahydroprenols that contain between 18 and 24 isoprene residues per molecule. Each prenol contains two trans residues, three saturated residues (alpha, omega and psi) and an exo-methylene substituent on the carbon atom beta to the isopropyl group in each omega-residue. The ubiquinone complex consisted of 90% ubiquinone-9, 9% ubiquinone-8 and 1% ubiquinone-10. The amount of polyprenol complex present reached a maximum of 1.7mg/culture bottle after 9-10 days of growth, coincident with the maximum weight of mycelium. The amount of ergosterol (10mg/culture bottle) and ubiquinone (1mg/culture bottle) reached a peak at 8 days. By the 13th day of growth the yield of ergosterol had fallen by 20% and that of ubiquinone by 85%. A study of the incorporation of [2-(14)C]mevalonate over different time-intervals confirmed that there was a slow turnover of prenol, a more rapid turnover of ergosterol and a very rapid turnover of ubiquinone. At any one time each member of the prenol complex had essentially the same specific radioactivity as other members of the complex. A similar conclusion was made about the ubiquinone mixture. Just over half of the polyprenol present was esterified to fatty acids. Subcellular fractionation studies indicated that the unesterified prenol is associated primarily with a mitochondrial fraction, whereas the ester is more widely distributed.

Growth of Aspergillus niger in the presence of [2-(14)C]mevalonate and (32)P(i) led to the formation of a lipid, containing (14)C (0.14% of dose) and (32)P (0.009% of dose), that had chromatographic properties identical with those of exo-methylene-hexahydropolyprenol phosphate. When a particulate enzyme preparation from the thallus of A. niger was incubated with GDP-[(14)C]mannose, the main radioactive products were mannose 1-phosphate (57% of products) and mannose (18%). In addition radioactive mannan (8%) and a mannolipid (2%) were formed. The latter was identified as exo-methylene-hexahydropolyprenol phosphate mannose on the basis of its chromatographic properties, acid lability and on the increase in formation of the mannolipid when the phosphate of exo-methylene-hexahydropolyprenols was added to the incubation mixture. The phosphates of ficaprenols and cetyl alcohol caused no corresponding increase. These observations are interpreted as evidence that the thallus of A. niger contains a mannose transferase that uses the phosphate of exo-methylene-hexahydropolyprenols as an acceptor. This situation is discussed in the light of the analogous involvement of a prenol phosphate mannose as an intermediate in the biosynthesis of bacterial wall mannan.