title: On the mechanism of the lycopene isomerase/cyclase reaction in Narcissus pseudonarcissus L. chromoplasts.
abstract: The lycopene cyclase reaction was investigated in Narcissus pseudonarcissus L. membranes using the terminal desaturation product of the system, 7,9,9',7'-tetra-cis-lycopene (prolycopene) as substrate. The enzymatically formed bicyclic carotenes were trans configured, so the overall reaction consists of two individual processes, isomerization and cyclization. The two reactions were experimentally distinguished by use of the inhibitor [2-(p-chlorophenylthio)triethylammonium chloride. NADPH, the essential cofactor for the overall reaction, originates from the plastid glycolytic pathway. It is shown that NADPH exhibits its function at the stage of isomerization and is also able to promote reduction of the prolycopene substrate in vitro.
authors.affiliation: Institut für Biologie II, Universität Freiburg, Federal Republic of Germany.
authors.forename: P
authors.initials: P
authors.lastname: Beyer
authors.forename: U
authors.initials: U
authors.lastname: Kröncke
authors.forename: V
authors.initials: V
authors.lastname: Nievelstein
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003067:Coenzymes / Q000378:metabolism; D005021:Ethylamines / Q000494:pharmacology; D019753:Intramolecular Lyases; D007535:Isomerases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D000077276:Lycopene; D009249:NADP / Q000378:metabolism; D015388:Organelles / Q000201:enzymology*; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology
chemical_list: D003067:Coenzymes; D005021:Ethylamines; C007143:2-(4-chlorophenylthio)triethylamine; D002338:Carotenoids; D009249:NADP; D007535:Isomerases; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase; D000077276:Lycopene