A Supramolecular Enzyme Mimic That Catalyzes the 15,15′ Double Bond Scission of β,β-Carotene
✍ Scribed by Richard R. French; Philipp Holzer; Michele G. Leuenberger; Wolf-D. Woggon
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 110 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
Dedicated to Professor Albert Eschenmoser on the occasion of his 75th birthday
The enzymes (carotene dioxygenases, CDOs) that cleave b,b-carotene 1 to provide retinal 2 as a precursor for retinol (vitamin A) are of significance to animal and human nutrition. To date two modes of cleavage of 1 have been proposed: 1) the more recently discovered excentric cleavage which yields apocarotenals, which can be degraded to 2 by boxidation, and 2) the central cleavage of 1 which gives retinal 2 directly (Scheme 1). [2, 3] The CDO enzymes responsible for CHO 15 15' Central Cleavage 1 2 14' 12' 10' 8' Scheme 1.
catalyzing these reactions have been neither purified nor are their respective co-factors known. Results concerning central cleavage suggest that the enzyme involved places its active sites metal complex directly above the C(15)C(15') bond. [4, 5] The fact that this CDO controls the regiospecific cleavage of one CC bond out of a possible six within the substrate is an intriguing and challenging one.
To mimic such a regioselective system the following strategy was employed. a) The synthesis of a receptor for 1 for which the binding constant K a for 1 is orders of magnitude greater than that for retinal 2 was necessary in order to prevent product inhibition. b) The introduction of a reactive metal center which is capable of cleaving E-configured, conjugated double bonds to aldehydes. c) The use of a co-