CloR, a bifunctional non-heme iron oxygenase involved in clorobiocin
biosynthesis.
J Biol Chem, 278 (33):
30661--30668 (August 2003)DOI: 10.1074/jbc.M303190200
Abstract
The aminocoumarin antibiotics novobiocin and clorobiocin contain a
3-dimethylallyl-4-hydroxybenzoate (3DMA-4HB) moiety. The biosynthesis
of this moiety has now been identified by biochemical and molecular
biological studies. CloQ from the clorobiocin biosynthetic gene
cluster in Streptomyces roseochromogenes DS 12976 has recently been
identified as a 4-hydroxyphenylpyruvate-3-dimethylallyltransferase.
In the present study, the enzyme CloR was overexpressed in Escherichia
coli, purified, and identified as a bifunctional non-heme iron oxygenase,
which converts 3-dimethylallyl-4-hydroxyphenylpyruvate (3DMA-4HPP)
via 3-dimethylallyl-4-hydroxymandelic acid (3DMA-4HMA) to 3DMA-4HB
by two consecutive oxidative decarboxylation steps. In 18O2 labeling
experiments we showed that two oxygen atoms are incorporated into
the intermediate 3DMA-4HMA in the first reaction step, but only
one further oxygen is incorporated into the final product 3DMA-4HB
during the second reaction step. CloR does not show sequence similarity
to known oxygenases. It apparently presents a novel member of the
diverse family of the non-heme iron (II) and alpha-ketoacid-dependent
oxygenases, with 3DMA-4HPP functioning both as an alpha-keto acid
and as a hydroxylation substrate. The reaction catalyzed by CloR
represents a new pathway for the formation of benzoic acids in nature.