Trypanosoma cruzi trans-sialidase operates through a covalent sialyl-enzyme intermediate: tyrosine is the catalytic nucleophile.

@article{Watts2003TrypanosomaCT,
  title={Trypanosoma cruzi trans-sialidase operates through a covalent sialyl-enzyme intermediate: tyrosine is the catalytic nucleophile.},
  author={Andrew G. Watts and Iben Damager and Maria L Amaya and Alejandro Buschiazzo and Pedro M Alzari and Alberto Carlos C Frasch and Stephen G Withers},
  journal={Journal of the American Chemical Society},
  year={2003},
  volume={125 25},
  pages={7532-3}
}
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… CONTINUE READING