FIGURE 1.

Biosynthetic pathway of coenzyme Q₈ in E. coli. The numbering of the aromatic carbon atoms used throughout this study is shown on Q₈, and the octaprenyl tail is represented by R on carbon 3 of the different biosynthetic intermediates. The name of the enzymes catalyzing the reactions (each labeled with a lowercase letter) is indicated. The enzyme catalyzing the C5-hydroxylation (reaction c) is unknown (see full text for further details). Abbreviations for coenzyme Q₈ (Q₈), C6-demethoxy-Q₈ (DMQ₈), C1-demethyl-C6-demethoxy-Q₈ (DDMQ₈), 3-octaprenyl-4-hydroxybenzoic acid (OHB), and 3-octaprenylphenol (OPP) are underlined.