title: Diverse chalcone synthase superfamily enzymes from the most primitive vascular plant, Psilotum nudum.
abstract: Psilotum nudum Griseb is a pteridophyte and belongs to the single family (Psilotaceae) of the division, Psilophyta. Being the only living species of a once populated division, P. nudum is the most primitive vascular plant. Chalcone synthase (CHS; EC 2.3.1.74) superfamily enzymes are responsible for biosyntheses of diverse secondary metabolites, including flavonoids and stilbenes. Using a reverse transcription-polymerase chain reaction strategy, four CHS-superfamily enzymes (PnJ, PnI, PnL and PnP) were cloned from P. nudum, and heterologously expressed in Escherichia coli. These four enzymes of 396-406 amino acids showed sequence identity of > 50% among themselves and to other higher-plant CHS-superfamily enzymes. PnJ and PnP preferred p-coumaroyl-CoA and isovaleryl-CoA respectively, as starter CoA and catalyzed CHS-type ring formation, indicating that they are CHS and phlorisovalerophenone synthase, respectively. On the other hand, PnI and PnL preferred cinnamoyl-CoA as starter CoA and catalyzed stilbene synthase-type cyclization and thus were determined to be pinosylvin synthases (EC 2.3.1.146). In addition, PnE, which uniquely contains a glutamine in place of otherwise strictly conserved histidine, had no apparent in vitro catalytic activity. Phylogenetic analysis indicated that these P. nudum clones form a separate cluster together with Equisetum arvense CHS. This cluster of pteridophytes is located next to the cluster formed by pine (gymnosperm) enzymes, in agreement with their evolutionary relationships. Psilotum nudum represents a plant with the most diverse CHS-superfamily enzymes and this ability to diverge may have provided a survival edge during evolution.
authors.affiliation: Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamazaki
authors.forename: D Y
authors.initials: DY
authors.lastname: Suh
authors.forename: W
authors.initials: W
authors.lastname: Sitthithaworn
authors.forename: K
authors.initials: K
authors.lastname: Ishiguro
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Shibuya
authors.forename: Y
authors.initials: Y
authors.lastname: Ebizuka
authors.forename: U
authors.initials: U
authors.lastname: Sankawa
mesh_terms: D000217:Acyltransferases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000378:metabolism; D020829:Equisetum / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029624:Ferns / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005419:Flavonoids / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D013267:Stilbenes / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D005419:Flavonoids; D009097:Multienzyme Complexes; D010940:Plant Proteins; D013267:Stilbenes; D000217:Acyltransferases; C119535:phlorisovalerophenone synthase; C022674:stilbene synthase; C020141:flavanone synthetase