Mechanism of inactivation of ornithine transcarbamoylase by Nδ-(N′-sulfodiaminophosphinyl)-l-ornithine, a true transition state analogue? Crystal structure and implications for catalytic mechanism.

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The structural designation of the chirality of the tetrahedral carbon in the putative TS is incorrectly stated to be R. The chirality of the tetrahedral phosphorus in PSOrn was shown to be R, but because the P-N-S bridging nitrogen (in PSOrn) is structurally homologous to oxygen in TS then the order of priority of the substituents is consequently different. The observation of an R phosphorus in PSOrn actually implies a tetrahedral S carbon in TS. Page 20018, left column, lines 9–18 should read: A high energy state or any intermediate on the reaction pathway that approximates an S configuration could of course be stabilized by the very same set of hydrogen bonding interactions made by PSOrn with OTCase. An S configuration in the TS would result from a stereospecific nucleophilic attack. In this scenario, prepositioning may be accompanied by enzyme-mediated distortion of the planar carbonyl group of CP toward the final tetrahedral S configuration, sterically assisting nucleophilic attack by the lone electron pair from the nitrogen of Orn.