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Trypanosoma cruzi Trans-sialidase Operates through a Covalent Sialyl-Enzyme Intermediate: Tyrosine Is the Catalytic Nucleophile

Abstract : Modified sialic acid substrates have been used to label Trypanosoma cruzi trans-sialidase, demonstrating that the enzyme catalyses the transfer of sialic acid through a covalent glycosyl-enzyme intermediate, a mechanism common to most retaining glycosidases. Peptic digestion of labeled protein, followed by LC-MS/MS analysis of the digest, identified Tyr342 as the catalytic nucleophile. This is the first such example of a retaining glycosidase utilizing an aryl glycoside intermediate. It is suggested that this alternative choice of nucleophile is a consequence of the chemical nature of sialic acid. A Tyr/Glu couple is invoked to relay charge from a remote glutamic acid, thereby avoiding electrostatic repulsion with the sialic acid carboxylate group.
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Contributor : Alejandro Buschiazzo <>
Submitted on : Friday, April 24, 2020 - 11:50:01 PM
Last modification on : Thursday, May 14, 2020 - 1:27:22 AM

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Andrew Watts, Iben Damager, Maria Amaya, Alejandro Buschiazzo, Pedro Alzari, et al.. Trypanosoma cruzi Trans-sialidase Operates through a Covalent Sialyl-Enzyme Intermediate: Tyrosine Is the Catalytic Nucleophile. Journal of the American Chemical Society, American Chemical Society, 2003, 125 (25), pp.7532-7533. ⟨10.1021/ja0344967⟩. ⟨pasteur-02554098⟩

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