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Structural insights into the stereochemistry of the cyclooxygenase reaction


Cyclooxygenases are bifunctional enzymes that catalyse the first committed step in the synthesis of prostaglandins, thromboxanes and other eicosanoids1,2,3. The two known cyclooxygenases isoforms share a high degree of amino-acid sequence similarity1,2,3,4, structural topology5,6,7 and an identical catalytic mechanism1,2,3. Cyclooxygenase enzymes catalyse two sequential reactions in spatially distinct, but mechanistically coupled active sites8,9,10,11. The initial cyclooxygenase reaction converts arachidonic acid (which is achiral) to prostaglandin G2 (which has five chiral centres). The subsequent peroxidase reaction reduces prostaglandin G2 to prostaglandin H2. Here we report the co-crystal structures of murine apo-cyclooxygenase-2 in complex with arachidonic acid and prostaglandin. These structures suggest the molecular basis for the stereospecificity of prostaglandin G2 synthesis.

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Figure 1: Arachidonic acid bound to the cyclooxygenase active site of the His207Ala variant of COX-2 at 2.4 Å resolution.
Figure 2: COX-2 dimer interface solvent channel.
Figure 3: Arachidonate and prostaglandin bound to the cyclooxygenase active site of wild-type COX-2.
Figure 4: Stereo diagram of the models of AA (a) and PGH2 ( b) bound at the cyclooxygenase active site.

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We are grateful to M. C. Walker, R. Fletterick, T. Rydel, H.-S. Shieh, J. Pierce, P. C. Isakson and K. Seibert for substantive discussions. LC–MS experiments were performed by J. Muhammad. Figures were generated with RIBBONS (M. Carson). S.W.R. is the recipient of an Australian National Health and Medical Research Council C.J. Martin Fellowship.

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Correspondence to Ravi G. Kurumbail.

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Kiefer, J., Pawlitz, J., Moreland, K. et al. Structural insights into the stereochemistry of the cyclooxygenase reaction . Nature 405, 97–101 (2000).

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