Abstract
Quinolinate synthase (NadA) is an Fe4S4 cluster-containing dehydrating enzyme involved in the synthesis of quinolinic acid (QA), the universal precursor of the essential coenzyme nicotinamide adenine dinucleotide. The reaction catalyzed by NadA is not well understood, and two mechanisms have been proposed in the literature that differ in the nature of the molecule (DHAP or G-3P) that condenses with iminoaspartate (IA) to form QA. In this article, using biochemical approaches, we demonstrate that DHAP is the triose that condenses with IA to form QA. The capacity of NadA to use G-3P is due to its previously unknown triose phosphate isomerase activity.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Aspartic Acid / analogs & derivatives
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Aspartic Acid / metabolism
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Bacterial Proteins / chemistry
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Bacterial Proteins / metabolism
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Dihydroxyacetone Phosphate / metabolism
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Metabolic Networks and Pathways
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Models, Chemical
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Multienzyme Complexes / chemistry*
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Multienzyme Complexes / metabolism*
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NAD / biosynthesis
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Quinolinic Acid / metabolism
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Thermotoga maritima / enzymology
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Triose-Phosphate Isomerase / chemistry*
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Triose-Phosphate Isomerase / metabolism*
Substances
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Bacterial Proteins
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Multienzyme Complexes
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NAD
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Aspartic Acid
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quinolinic acid synthetase
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Dihydroxyacetone Phosphate
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iminoaspartic acid
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Triose-Phosphate Isomerase
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Quinolinic Acid