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Phylloquinone (vitamin K 1 ) biosynthesis in plants: two peroxisomal thioesterases of lactobacillales origin hydrolyze 1,4‐dihydroxy‐2‐naphthoyl‐coa
Author(s) -
Widhalm Joshua R.,
Ducluzeau AnneLise,
Buller Nicole E.,
Elowsky Christian G.,
Olsen Laura J.,
Basset Gilles J. C.
Publication year - 2012
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2012.04972.x
Subject(s) - thioesterase , arabidopsis , biochemistry , biology , arabidopsis thaliana , biosynthesis , metabolic engineering , peroxisome , enzyme , gene , mutant
Summary It is not known how plants cleave the thioester bond of 1,4‐dihydroxy‐2‐naphthoyl‐CoA (DHNA‐CoA), a necessary step to form the naphthoquinone ring of phylloquinone (vitamin K 1 ). In fact, only recently has the hydrolysis of DHNA‐CoA been demonstrated to be enzyme driven in vivo , and the cognate thioesterase characterized in the cyanobacterium Synechocystis . With a few exceptions in certain prokaryotic ( Sorangium and Opitutus ) and eukaryotic ( Cyanidium , Cyanidioschyzon and Paulinella ) organisms, orthologs of DHNA‐CoA thioesterase are missing outside of the cyanobacterial lineage. In this study, genomic approaches and functional complementation experiments identified two Arabidopsis genes encoding functional DHNA‐CoA thioesterases. The deduced plant proteins display low percentages of identity with cyanobacterial DHNA‐CoA thioesterases, and do not even share the same catalytic motif. GFP‐fusion experiments demonstrated that the Arabidopsis proteins are targeted to peroxisomes, and subcellular fractionations of Arabidopsis leaves confirmed that DHNA‐CoA thioesterase activity occurs in this organelle. In vitro assays with various aromatic and aliphatic acyl‐CoA thioester substrates showed that the recombinant Arabidopsis enzymes preferentially hydrolyze DHNA‐CoA. Cognate T‐DNA knock‐down lines display reduced DHNA‐CoA thioesterase activity and phylloquinone content, establishing in vivo evidence that the Arabidopsis enzymes are involved in phylloquinone biosynthesis. Extraordinarily, structure‐based phylogenies coupled to comparative genomics demonstrate that plant DHNA‐CoA thioesterases originate from a horizontal gene transfer with a bacterial species of the Lactobacillales order.