Glycobiology, 2000, Vol. 10, No. 2 213-221
© 2000 Oxford University Press
Trans-sialidase from Trypanosoma cruzi catalyzes sialoside hydrolysis with retention of configuration
Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, 21944970, Cidade Universitária, Rio de Janeiro, Brasil and 3Glycobiology Research and Training Center, School of Medicine, University of California San Diego, La Jolla, CA 920930687, USA
The trans-sialidase from Trypanosoma cruzi is a member of the sialidase superfamily that functions as a sialidase in the absence of a carbohydrate acceptor. We have used 1H nuclear magnetic resonance (NMR) spectroscopy to investigate the stereospecificity of the hydrolysis of two substrates, namely, 4-methyl-umbelliferyl-N-acetylneuraminic acid and
(23)-sialyllactose, catalyzed by a recombinant T.cruzi trans-sialidase. We demonstrate that, in aqueous solution, the thermodynamically less stable
-form of N-acetylneuraminic acid is the initial product of the hydrolysis; subsequent mutarotation leads eventually to an equilibrium mixture of the
and ß forms, in molar ratio 8:92. In a mixed water/methanol solution, the hydrolysis reaction produces also the
-methyl sialoside but not its ß-methyl counterpart. We also show that 4-methyl-umbelliferyl-N-acetylneuraminic acid is a significantly better substrate for the sialidase than
(23)-sialyllactose. Prolonged incubation of
(23)-sialyllactose with an excess of trans-sialidase produced a trace of 2-deoxy-2,3-didehydro-N-acetylneuraminic acid, as identified by NMR spectroscopy and by gas liquid chromatography/mass spectrometry. In conclusion, this study shows that the stereoselectivity of the sialidase activity of T.cruzi trans-sialidase is identical to that of bacterial, viral, and mammalian sialidases, suggesting a similar active-site architecture.
1 To whom correspondence should be addressed
2 Present address: CMM-East Building, Suite 1056, 9500 Gilman Drive, M/C 0687, University of California at San Diego, La Jolla, CA 920930687
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