title: Partial purification and characterization of a monoterpene cyclase, limonene synthase, from the liverwort Ricciocarpos natans.
abstract: 4S-(-)-limonene is the major monoterpene accumulated by the liverwort Ricciocarpos natans, and a cell-free extract from this nonvascular plant cultured in vitro catalyzes the cyclization of geranyl diphosphate to limonene. The time course of limonene synthase activity parallels cultured growth but shows a maximum in specific activity in the lag phase following transfer to fresh medium. The operationally soluble enzyme was partially purified by combination of anion-exchange and hydroxylapatite chromatography. The limonene synthase from R. natans possesses a molecular weight of about 51,000, exhibits a pH optimum at 6.5, a pI at 5.3, and a requirement for either Mg2+ or Mn2+ as cofactor, and appears to employ 3S-linalyl disphosphate as a bound intermediate in the cyclization of the geranyl substrate (Km approximately 1.25 microM). In stereochemistry of the coupled isomerization-cyclization reaction and in general properties, the limonene synthase from this bryophyte resembles the corresponding monoterpene cyclases from gymnosperm and angiosperm species.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman 99164-6340, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Adam
authors.forename: J
authors.initials: J
authors.lastname: Crock
authors.forename: R
authors.initials: R
authors.lastname: Croteau
mesh_terms: D053138:Cyclohexenes; D006863:Hydrogen-Ion Concentration; D019753:Intramolecular Lyases; D007535:Isomerases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D000077222:Limonene; D008970:Molecular Weight; D063245:Plant Development; D010944:Plants / Q000201:enzymology*; D013729:Terpenes / Q000737:chemistry / Q000378:metabolism
chemical_list: D053138:Cyclohexenes; D013729:Terpenes; D000077222:Limonene; D007535:Isomerases; D019753:Intramolecular Lyases; C040265:pinene cyclase I