Carotenoids carry out a variety of critical functions in all forms of life. In plants they operate as accessory light-harvesting components (antenna complex) of photosynthetic systems, light induced antioxidants, membrane fluidity regulators, and pigments (yellow to red-orange; important in attracting pollinators). In animals, carotenoids yield essential precursors necessary for vision, embryonic development, cellular homeostasis, and immunity (Vitamin A). Since vitamin A is not synthesized de novo in animals, it is necessary to consume preformed vitamin A (retinyl esters) from other sources or as provitamin A compounds found in vegetables and fruits. Carotenoid Cleavage Dioxygenases (CCDs) are enzymes capable of producing carotenoid derivatives (apocarotenoids). They are found in all forms of life. They generally catalyze the cleavage of carotenoid carbon-carbon double bonds. CCDs possess a nonheme group in their active sites. The ferrous ion is coordinated to 4 histidine nitrogens in a “see-saw” geometry. In this work, we will probe the structure-reactivity relationship for the CCD active sites using small molecule model compounds. We have synthesized a series iron(II) compounds coordinated to 4 histidine mimics (imidazole) in various geometries. The complexes have been characterized by X-ray crystallography, Mössbauer spectroscopy, electrochemistry, and DFT.

Synthetic model systems for alkene dioxygenase

2019 Spring National Meeting

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