The carotenase AtCCD1 from Arabidopsis thaliana is a dioxygenase

J Biol Chem. 2006 Apr 14;281(15):9845-51. doi: 10.1074/jbc.M511668200. Epub 2006 Feb 3.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / enzymology*
  • Binding Sites
  • Chromatography, Gas
  • Chromatography, Liquid
  • Chromatography, Thin Layer
  • Cloning, Molecular
  • Dioxygenases / chemistry*
  • Dioxygenases / genetics
  • Gene Expression Regulation, Plant
  • Magnetic Resonance Spectroscopy
  • Mass Spectrometry
  • Models, Chemical
  • Oxygen / chemistry*
  • Oxygen / metabolism
  • Oxygenases / chemistry*
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry

Substances

  • Recombinant Proteins
  • Oxygenases
  • Dioxygenases
  • carotenoid cleavage dioxygenase 1
  • Oxygen