A soluble, magnesium-independent prenyltransferase catalyzes reverse and regular C-prenylations and O-prenylations of aromatic substrates

Fnq26 from Streptomyces cinnamonensis DSM 1042 is a new member of the recently identified CloQ/Orf2 class of prenyltransferases. The enzyme was overexpressed in E. coli and purified to apparent homogeneity, resulting in a soluble, monomeric protein of 33.2 kDa. The catalytic activity of Fnq26 is independent of the presence of Mg2+ or other divalent metal ions. With flaviolin (2,5,7-trihydroxy-1,4-naphthoquinone) as substrate, Fnq26 catalyzes the formation of a carbon–carbon-bond between C-3 (rather than C-1) of geranyl diphosphate and C-3 of flaviolin, i.e. an unusual “reverse” prenylation. With 1,3-dihydroxynaphthalene and 4-hydroxybenzoate as substrates Fnq26 catalyzes O-prenylations.