Publications

• Phylloquinone (vitamin K(1)) biosynthesis in plants: two peroxisomal thioesterases of Lactobacillales origin hydrolyze 1,4-dihydroxy-2-naphthoyl-CoA.

  Widhalm J.R., Ducluzeau A.-L., Buller N.E., Elowsky C.G., Olsen L.J., Basset G.J.C.

  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 ... >> More

  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. << Less

  Plant J. 71:205-215(2012) [PubMed] [EuropePMC]

• A dedicated thioesterase of the Hotdog-fold family is required for the biosynthesis of the naphthoquinone ring of vitamin K1.

  Widhalm J.R., van Oostende C., Furt F., Basset G.J.C.

  Phylloquinone (vitamin K(1)) is a bipartite molecule that consists of a naphthoquinone ring attached to a phytyl side chain. The coupling of these 2 moieties depends on the hydrolysis of the CoA thioester of 1,4-dihydroxy-2-naphthoate (DHNA), which forms the naphthalenoid backbone. It is not known ... >> More

  Phylloquinone (vitamin K(1)) is a bipartite molecule that consists of a naphthoquinone ring attached to a phytyl side chain. The coupling of these 2 moieties depends on the hydrolysis of the CoA thioester of 1,4-dihydroxy-2-naphthoate (DHNA), which forms the naphthalenoid backbone. It is not known whether such a hydrolysis is enzymatic or chemical. In this study, comparative genomic analyses identified orthologous genes of unknown function that in most species of cyanobacteria cluster with predicted phylloquinone biosynthetic genes. The encoded approximately 16-kDa proteins display homology with some Hotdog domain-containing CoA thioesterases that are involved in the catabolism of 4-hydroxybenzoyl-CoA and gentisyl-CoA (2,5-dihydroxybenzoyl-CoA) in certain soil-dwelling bacteria. The Synechocystis ortholog, encoded by gene slr0204, was expressed as a recombinant protein and was found to form DHNA as reaction product. Unlike its homologs in the Hotdog domain family, Slr0204 showed strict substrate specificity. The Synechocystis slr0204 knockout was devoid of DHNA-CoA thioesterease activity and accumulated DHNA-CoA. As a result, knockout cells contained 13-fold less phylloquinone than their wild-type counterparts and displayed the typical photosensitivity to high light associated to phylloquinone deficiency in cyanobacteria. << Less

  Proc. Natl. Acad. Sci. U.S.A. 106:5599-5603(2009) [PubMed] [EuropePMC]