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The carotenase AtCCD1 from Arabidopsis thaliana is a dioxygenase.

J Biol Chem. 2006 Apr 14;281(15):9845-51. Epub 2006 Feb 03
Holger Schmidt 1 , Robert Kurtzer , Wolfgang Eisenreich , Wilfried Schwab
Holger Schmidt 1 , Robert Kurtzer , Wolfgang Eisenreich , Wilfried Schwab

[No authors listed]

Author information
  • 1 Foundation for Biomolecular Food Technology, Technische Universität München, Lise-Meitner-Strasse 34, D-84354 Freising, Germany. holger.schmidt@mytum.de

摘要


Apocarotenoids resulting from the oxidative cleavage of carotenoids serve as important signaling and accessory molecules in a variety of biological processes. The enzymes catalyzing these reactions are referred to as carotenases or carotenoid oxygenases. Whether they act according to a monooxygenase mechanism, requiring two oxygens from different sources, or a dioxygenase mechanism is still a topic of controversy. In this study, we utilized the readily available beta-apo-8'-carotenal as a substrate for the heterologously expressed AtCCD1 protein from Arabidopsis thaliana to investigate the oxidative cleavage mechanism of the 9,10 double bond of carotenoids. Beta-ionone and a C(17)-dialdehyde were detected as products by gas and liquid chromatography-mass spectrometry as well as NMR analysis. Labeling experiments using H(2)(18)O or (18) O(2) showed that the oxygen in the keto-group of beta-ionone is derived solely from molecular dioxygen. When experiments were performed in an (18)O(2)-enriched atmosphere, a substantial fraction of the C(17)-dialdehyde contained labeled oxygen. The results unambiguously demonstrate a dioxygenase mechanism for the carotenase AtCCD1 from A. thaliana.