HlPT-1, a membrane-bound prenyltransferase responsible for the biosynthesis of bitter acids in hops

Biochem Biophys Res Commun. 2012 Jan 6;417(1):393-8. doi: 10.1016/j.bbrc.2011.11.125. Epub 2011 Dec 7.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Membrane / enzymology*
  • Cyclohexenes / metabolism*
  • Dimethylallyltranstransferase / chemistry
  • Dimethylallyltranstransferase / metabolism*
  • Humulus / enzymology*
  • Substrate Specificity
  • Terpenes / metabolism*

Substances

  • Cyclohexenes
  • Terpenes
  • lupulon
  • Dimethylallyltranstransferase
  • humulon