| STRUCTURE |
Closer to a Diels-Alderase? The crystal structure of macrophomate synthase (MPS), a protein believed to catalyze a Diels-Alder reaction between a diene and a dienophile to form an aromatic compound, has been determined [Nature, 422, 185 (2003)]. There is a high level of interest in natural Diels-Alderases because they may provide insights into how reactions in solutions might be better controlled. And because the transition state in a Diels-Alder reaction closely resembles the product, a natural Diels-Alderase should present a way to overcome product inhibition. The crystal structure--solved by Isao Tanaka, Hideaki Oikawa, and coworkers at Hokkaido University, Sapporo, Japan--explains how MPS generates the dienophile and holds it in place with the diene for the addition reaction. The addition product is subsequently decarboxylated and dehydrated to the final aromatic product. In this way, product inhibition is avoided. The addition product may arise from a concerted cycloaddition (Diels-Alder reaction) or a stepwise addition. The crystal structure does not distinguish between these two possibilities. If MPS turns out to be a Diels-Alderase, it would be the first such enzyme to be structurally characterized. |
| UPDATE | 03.03 |
| AUTHOR |
Hokkaido University - Oikawa Hideaki - Tanaka Isao |
| LITERATURE REF. | [Nature, 422, 185 (2003)]. |
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