title: The bifurcation of the cyanogenic glucoside and glucosinolate biosynthetic pathways.
abstract: The biosynthetic pathway for the cyanogenic glucoside dhurrin in sorghum has previously been shown to involve the sequential production of (E)- and (Z)-p-hydroxyphenylacetaldoxime. In this study we used microsomes prepared from wild-type and mutant sorghum or transiently transformed Nicotiana benthamiana to demonstrate that CYP79A1 catalyzes conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime whereas CYP71E1 catalyzes conversion of (E)-p-hydroxyphenylacetaldoxime into the corresponding geometrical Z-isomer as required for its dehydration into a nitrile, the next intermediate in cyanogenic glucoside synthesis. Glucosinolate biosynthesis is also initiated by the action of a CYP79 family enzyme, but the next enzyme involved belongs to the CYP83 family. We demonstrate that CYP83B1 from Arabidopsis thaliana cannot convert the (E)-p-hydroxyphenylacetaldoxime to the (Z)-isomer, which blocks the route towards cyanogenic glucoside synthesis. Instead CYP83B1 catalyzes the conversion of the (E)-p-hydroxyphenylacetaldoxime into an S-alkyl-thiohydroximate with retention of the configuration of the E-oxime intermediate in the final glucosinolate core structure. Numerous microbial plant pathogens are able to detoxify Z-oximes but not E-oximes. The CYP79-derived E-oximes may play an important role in plant defense.
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|VILLUM Research Center for 'Plant Plasticity', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Clausen
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|Center for Synthetic Biology 'bioSYNergy', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
authors.forename: Rubini M
authors.initials: RM
authors.lastname: Kannangara
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|VILLUM Research Center for 'Plant Plasticity', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|Center for Synthetic Biology 'bioSYNergy', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
authors.forename: Carl E
authors.initials: CE
authors.lastname: Olsen
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Vic., Australia.
authors.forename: Cecilia K
authors.initials: CK
authors.lastname: Blomstedt
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Vic., Australia.
authors.forename: Roslyn M
authors.initials: RM
authors.lastname: Gleadow
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|VILLUM Research Center for 'Plant Plasticity', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|Center for Synthetic Biology 'bioSYNergy', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Jørgensen
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Bak
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|VILLUM Research Center for 'Plant Plasticity', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|Center for Synthetic Biology 'bioSYNergy', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
authors.forename: Mohammed S
authors.initials: MS
authors.lastname: Motawie
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|VILLUM Research Center for 'Plant Plasticity', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|Center for Synthetic Biology 'bioSYNergy', Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.|Carlsberg Laboratory, 10 Gamle Carlsberg Vej, DK-1799, Copenhagen V, Denmark.
authors.forename: Birger Lindberg
authors.initials: BL
authors.lastname: Møller
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D005961:Glucosinolates / Q000378:metabolism*; D007536:Isomerism; D009154:Mutation; D010091:Oximes / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D045868:Sorghum / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D005961:Glucosinolates; D010091:Oximes; D010940:Plant Proteins; C020363:4-hydroxyphenylacetaldoxime; D014443:Tyrosine; D003577:Cytochrome P-450 Enzyme System; C431937:CYP83B1 protein, Arabidopsis; C089817:cytochrome P450TYR; C110889:cytochrome P-450 CYP71E1 (sorghum)
keywords: CYP71E1; CYP79A1; CYP83B1; E- and Z-oxime metabolism; Sinapis alba; Sorghum bicolor; cytochrome P450; microbial Z-oxime-nitrile pathway; nitriles; oxime dehydration