Alternative hydroxylases for the aerobic and anaerobic biosynthesis of ubiquinone in Escherichia coli

Biochemistry. 1978 Oct 31;17(22):4750-5. doi: 10.1021/bi00615a024.


The synthesis of ubiquinone under anaerobic conditions was examined in a variety of strains of Escherichia coli K12. All were shown to synthesize appreciable quantities of ubiquinone 8 when grown anaerobically on glycerol in the presence of fumarate. Under these conditions, ubiquinone 8 was in most cases the principal quinone formed, and levels in the range 50--70% of those obtained aerobically were observed. Studies with mutants blocked in the various reactions of the aerobic pathway for ubiquinone 8 synthesis established that under anaerobic conditions three alternative hydroxylation reactions not involving molecular oxygen are used to derive the C-4, -5, and -6 oxygens of ubiquinone 8. Thus, mutants blocked in either of the three hydroxylation reactions of the aerobic pathway (ubiB, ubiH, or ubiF) are each able to synthesize ubiquinone 8 anaerobically, whereas mutants lacking the octaprenyltransferase (ubiA), carboxy-lyase (ubiD), or methyltransferases (ubiE or ubiG) of the aerobic pathway remain blocked anaerobically. The demonstration that E. coli possesses a special mechanism for the anaerobic biosynthesis of ubiquinone suggests that this quinone may play an important role in anaerobic metabolism.

Publication types

  • Comparative Study

MeSH terms

  • Aerobiosis
  • Anaerobiosis
  • Escherichia coli / enzymology*
  • Fumarates / metabolism
  • Genotype
  • Mixed Function Oxygenases / metabolism*
  • Species Specificity
  • Ubiquinone / biosynthesis*


  • Fumarates
  • Ubiquinone
  • Mixed Function Oxygenases