Cyclopropylglyoxylate as a mechanistic probe of thiamine pyrophosphate dependent pyruvate-metabolizing enzymes |
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| Authors: | David J. Livingston Spencer L. Shames Robert Gennis Christopher T. Walsh |
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| Affiliation: | 1. Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, North Third Ring Road 15, Chaoyang District, 100029 Beijing, China;2. Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Denickestrasse 15, D-21073 Hamburg, Germany;1. Department of Food, Environmental and Nutritional Sciences (DEFENS), University of Milan, Via Mangiagalli 25, 20133 Milan, Italy;2. Department of Organic and Inorganic Chemistry, Federal University of Ceará, Campus do Pici, Postal Box 6044, 60455-970 Fortaleza, Ceará, Brazil |
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| Abstract: | Four pyruvate-decarboxylating enzymes with thiamine pyrophosphate (TPP) cofactors catalyze the decarboxylation of the cyclopropyl substrate analog cyclopropylglyoxylate. Pyruvate: ferredoxin oxidoreductase, an archaebacterial enzyme which catalyzes oxidation of the hydroxyethyl-TPP (HETPP) intermediate by two one-electron transfers to an iron-sulfur center, generates the coenzyme A thioester of cyclopropylcarboxylic acid. A long-lived free radical, HETPP is thought to be an intermediate in the pyruvate to acetyl-CoA conversion; however, cleavage of the cyclopropyl ring was not detected. Pyruvate decarboxylase, pyruvate oxidase, and pyruvate dehydrogenase also generate the corresponding cyclopropyl products. The applicability of cyclopropyl substrate analogs as indicators of free-radical enzyme mechanisms is discussed in light of these results. |
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