title: HlPT-1, a membrane-bound prenyltransferase responsible for the biosynthesis of bitter acids in hops.
abstract: Female flowers of hop (Humulus lupulus L.) develop a large number of glandular trichomes called lupulin glands that contain a variety of prenylated compounds such as α- and β-acid (humulone and lupulone, respectively), as well as xanthohumol, a chalcone derivative. These prenylated compounds are biosynthesized by prenyltransferases catalyzing the transfer of dimethylallyl moiety to aromatic substances. In our previous work, we found HlPT-1 a candidate gene for such a prenyltransferase in a cDNA library constructed from lupulin-enriched flower tissues. In this study, we have characterized the enzymatic properties of HlPT-1 using a recombinant protein expressed in baculovirus-infected insect cells. HlPT-1 catalyzed the first transfer of dimethylallyl moiety to phloroglucinol derivatives, phlorisovalerophenone, phlorisobutyrophenone and phlormethylbutanophenone, leading to the formation of humulone and lupulone derivatives. HlPT-1 also recognized naringenin chalcone as a flavonoid substrate to yield xanthohumol, and this broad substrate specificity is a unique character of HlPT-1 that is not seen in other reported flavonoid prenyltransferases, all of which show strict specificity for their aromatic substrates. Moreover, unlike other aromatic substrate prenyltransferases, HlPT-1 revealed an exclusive requirement for Mg(2+) as a divalent cation for its enzymatic activity and also showed exceptionally narrow optimum pH at around pH 7.0.
authors.affiliation: Laboratory of Plant Gene Expression, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tsurumaru
authors.forename: Kanako
authors.initials: K
authors.lastname: Sasaki
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Miyawaki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Uto
authors.forename: Takayuki
authors.initials: T
authors.lastname: Momma
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Umemoto
authors.forename: Masaki
authors.initials: M
authors.lastname: Momose
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yazaki
mesh_terms: D002462:Cell Membrane / Q000201:enzymology*; D053138:Cyclohexenes / Q000378:metabolism*; D004122:Dimethylallyltranstransferase / Q000737:chemistry / Q000378:metabolism*; D027582:Humulus / Q000201:enzymology*; D013379:Substrate Specificity; D013729:Terpenes / Q000378:metabolism*
chemical_list: D053138:Cyclohexenes; D013729:Terpenes; C008299:lupulon; D004122:Dimethylallyltranstransferase; C007966:humulon