Geraniol hydroxylase and hydroxygeraniol oxidase activities of the CYP76 family of cytochrome P450 enzymes and potential for engineering the early steps of the (seco)iridoid pathway

The geraniol-derived (seco)iridoid skeleton is a precursor for a large group of bioactive compounds with diverse therapeutic applications, including the widely used anticancer molecule vinblastine. Despite of this economic prospect, the pathway leading to iridoid biosynthesis from geraniol is still...

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Veröffentlicht in:Metabolic engineering 2013-11, Vol.20, p.221-232
Hauptverfasser: Höfer, René, Dong, Lemeng, André, François, Ginglinger, Jean-François, Lugan, Raphael, Gavira, Carole, Grec, Sebastien, Lang, Gerhard, Memelink, Johan, Van Der Krol, Sander, Bouwmeester, Harro, Werck-Reichhart, Danièle
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Sprache:eng
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Zusammenfassung:The geraniol-derived (seco)iridoid skeleton is a precursor for a large group of bioactive compounds with diverse therapeutic applications, including the widely used anticancer molecule vinblastine. Despite of this economic prospect, the pathway leading to iridoid biosynthesis from geraniol is still unclear. The first geraniol hydroxylation step has been reported to be catalyzed by cytochrome P450 enzymes such as CYP76B6 from Catharanthus roseus and CYP76C1 from Arabidopsis thaliana. In the present study, an extended functional analysis of CYP76 family members was carried-out to identify the most effective enzyme to be used for pathway reconstruction. This disproved CYP76C1 activity and led to the characterization of CYP76C4 from A. thaliana as a geraniol 9- or 8-hydroxylase. CYP76B6 emerged as a highly specialized multifunctional enzyme catalyzing two sequential oxidation steps leading to the formation of 8-oxogeraniol from geraniol. This dual function was confirmed in planta using a leaf-disc assay. The first step, geraniol hydroxylation, was very efficient and fast enough to outcompete geraniol conjugation in plant tissues. When the enzyme was expressed in leaf tissues, 8-oxogeraniol was converted into further oxidized and/or reduced compounds in the absence of the next enzyme of the iridoid pathway. •Arabidopsis CYP76C4 converts geraniol into 8-hydroxy- or 9-geraniol.•C. roseus CYP76B6 catalyzes successive oxidations of geraniol into 8-oxogeraniol.•Homology modeling provides an explanation for CYP76s regioselectivities.•Enzyme activities can be tested in planta using a transfected leaf-disc assay.•CYP76B6 activity outcompetes geraniol glycosidases in plant tissues.
ISSN:1096-7176
1096-7184
DOI:10.1016/j.ymben.2013.08.001