November 2009

Trapping the Elusive Michaelis

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Structure of the OxdRE binding cavity comparing the open (pink) and closed (blue) forms of the enzyme.

Many crystallographic attempts to trap a reaction intermediate within an enzyme result in a protein crystal that contains multiple intermediate compounds, leaving the structure of the true intermediate open to interpretation. The authors of this study managed to bypass this issue for Rhodococcus sp. N-771 aldoxime dehydratase (OxdRE) by reducing the substrate-bound ferric Oxd complex using X-ray radiation under cryogenic temperature, thus enabling them to drive the reaction completely to the intermediate. The result was a clean structure of an elusive Michaelis complex. A comparison with a known structure of OxdRE in the resting state provided insight into the mechanisms of substrate recognition and catalysis of a nitrile-producing enzyme. These results could have practical applications in industry, where the chemical synthesis of nitriles often involves harsh reaction conditions.



X-ray Crystal Structure of the Michaelis Complex of Aldoxime Dehydratase

Hitomi Sawai, Hiroshi Sugimoto, Yasuo Kato, Yasuhisa Asano, Yoshitsugu Shiro, and Shigetoshi Aono

J. Biol. Chem., published online Sept. 8, 2009

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