Journal of the American Chemical Society
Communication
5
are two half-chair (6H5 and H6) and two boat (4,OB and B4,O
)
ACKNOWLEDGMENTS
■
conformations (Figure S2). We suggest that, for the influenza
enzyme, the glycal inhibitor binds in a 6H5 half-chair
conformation and that the interaction of the 4-substituent
with the enzyme gives rise to no stabilization of the
glycosylation TS as the Michaelis complex undergoes reaction
to give the enzyme-bound intermediate in a 2C5 chair
conformation.15
The above analysis also explains reactivity differences for
sialosyl-enzyme covalent intermediates formed between a series
of influenza viral enzymes and 4-substituted 2,3-difluorosialic
acids.29 That is, the fluorinated sialosyl-enzyme intermediates
(see Scheme 1 for the generic structure) containing either a
guanidino or amino group at C-4 undergo deglycosylation at
greatly reduced rates compared to the 4-OH derivative. This
effect likely arises from nonproductive binding of the 4-
substituent that is expressed at the enzyme-bound intermediate
but not at the deglycosylation TS, thus resulting in the sialosyl-
enzyme intermediate being longer lived for the positively
charged inhibitors.29
This work was aided by a Natural Sciences and Engineering
Research Council of Canada Discovery grant to A.J.B. (121348-
2007).
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ASSOCIATED CONTENT
* Supporting Information
■
S
Complete ref 2; experimental procedures and characterization
of compounds; plots of log(Km/kcat) versus log(Ki) for the
enzyme-catalyzed reactions; and conformational itinerary maps.
This material is available free of charge via the Internet at
AUTHOR INFORMATION
Corresponding Author
(27) Henrissat, B.; Bairoch, A. Biochem. J. 1996, 316, 695−696.
(28) Raab, M.; Tvaroska, I. J. Mol. Model. 2011, 17, 1445−1456.
̌
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Buchini, S.; Watts, A. G.; Pilling, P.; Streltsov, V. A.; Petric, M.;
Liggins, R.; Barrett, S.; McKimm-Breschkin, J. L.; Niikura, M.; Withers,
S. G. Science 2013, 340, 71−75.
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Present Address
†J.N.W.: Northern Catalyst Scientific Consulting, 279 Silbrass
Private, Ottawa, ON K2J 5M6, Canada
Notes
The authors declare no competing financial interest.
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dx.doi.org/10.1021/ja405916q | J. Am. Chem. Soc. XXXX, XXX, XXX−XXX