title: A Dedicated Type II NADPH Dehydrogenase Performs the Penultimate Step in the Biosynthesis of Vitamin K1 in Synechocystis and Arabidopsis.
abstract: Mutation of Arabidopsis thaliana NAD(P)H DEHYDROGENASE C1 (NDC1; At5g08740) results in the accumulation of demethylphylloquinone, a late biosynthetic intermediate of vitamin K1. Gene coexpression and phylogenomics analyses showed that conserved functional associations occur between vitamin K biosynthesis and NDC1 homologs throughout the prokaryotic and eukaryotic lineages. Deletion of Synechocystis ndbB, which encodes for one such homolog, resulted in the same defects as those observed in the cyanobacterial demethylnaphthoquinone methyltransferase knockout. Chemical modeling and assay of purified demethylnaphthoquinone methyltransferase demonstrated that, by virtue of the strong electrophilic nature of S-adenosyl-l-methionine, the transmethylation of the demethylated precursor of vitamin K is strictly dependent on the reduced form of its naphthoquinone ring. NDC1 was shown to catalyze such a prerequisite reduction by using NADPH and demethylphylloquinone as substrates and flavine adenine dinucleotide as a cofactor. NDC1 displayed Michaelis-Menten kinetics and was markedly inhibited by dicumarol, a competitive inhibitor of naphthoquinone oxidoreductases. These data demonstrate that the reduction of the demethylnaphthoquinone ring represents an authentic step in the biosynthetic pathway of vitamin K, that this reaction is enzymatically driven, and that a selection pressure is operating to retain type II NAD(P)H dehydrogenases in this process.
authors.affiliation: Department of Agronomy and Horticulture, and Center for Plant Science Innovation, University of Nebraska, Lincoln, Nebraska 68588.
authors.forename: Abdelhak
authors.initials: A
authors.lastname: Fatihi
authors.affiliation: Department of Agronomy and Horticulture, and Center for Plant Science Innovation, University of Nebraska, Lincoln, Nebraska 68588.
authors.forename: Scott
authors.initials: S
authors.lastname: Latimer
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schmollinger
authors.affiliation: Department of Agronomy and Horticulture, and Center for Plant Science Innovation, University of Nebraska, Lincoln, Nebraska 68588.
authors.forename: Anna
authors.initials: A
authors.lastname: Block
authors.affiliation: Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588.
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Dussault
authors.affiliation: School of Life Sciences and Center for the Study of Early Events in Photosynthesis, Arizona State University, Tempe, Arizona 85287.
authors.forename: Wim F J
authors.initials: WF
authors.lastname: Vermaas
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095 Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095.
authors.forename: Sabeeha S
authors.initials: SS
authors.lastname: Merchant
authors.affiliation: Department of Agronomy and Horticulture, and Center for Plant Science Innovation, University of Nebraska, Lincoln, Nebraska 68588 gbasset2@unl.edu.
authors.forename: Gilles J
authors.initials: GJ
authors.lastname: Basset
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005810:Multigene Family; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010837:Vitamin K 1 / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D010837:Vitamin K 1; D009247:NADH, NADPH Oxidoreductases; C561934:NDC1 protein, Arabidopsis