title: Role of reducing co-factor in cerulenin-insensitivity of 6-hydroxymellein synthase in carrot cell extract.
abstract: The activity of 6-hydroxymellein synthase, a multifunctional polyketide biosynthetic enzyme of carrot, was not inhibited by cerulenin in the presence of NADPH. However, cerulenin showed a marked inhibitory activity to the synthase if the reducing co-factor was omitted from the assay mixture. The synthase was also sensitive to the antibiotic even in the presence of NADPH when the acyl condensation site and the reducing domain at the reaction center of the enzyme were dissociated under the high ionic strength condition. In addition, the synthase activity was appreciably inhibited when NADH was employed instead of NADPH. These observations strongly suggest that a phosphate group attached to 2'-position of adenosyl moiety of NADPH molecule plays an important role in the apparent insensitivity of 6-hydroxymellein synthase toward cerulenin.
authors.affiliation: Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Sugitani, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Kurosaki
authors.forename: K
authors.initials: K
authors.lastname: Togashi
authors.forename: M
authors.initials: M
authors.lastname: Arisawa
mesh_terms: D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D002569:Cerulenin / Q000494:pharmacology*; D018552:Daucus carota / Q000201:enzymology*; D004790:Enzyme Induction; D007700:Kinetics; D008025:Ligases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D010936:Plant Extracts; D018517:Plant Roots
chemical_list: D009097:Multienzyme Complexes; D010936:Plant Extracts; D009243:NAD; D002569:Cerulenin; D009249:NADP; D010088:Oxidoreductases; D000217:Acyltransferases; C070623:6-hydroxymellein synthetase; D008025:Ligases