The Aspergillus fumigatus sialidase is a 3-deoxy-D-glycero-D-galacto-2- nonulosonic acid hydrolase (KDNase): Structural and mechanistic insights

Judith C. Telford, Juliana H.F. Yeung, Guogang Xu, Milton J. Kiefel, Andrew G. Watts, Stefan Hader, Jefferson Chan, Andrew J. Bennet, Margo M. Moore, Garry L. Taylor

Research output: Contribution to journalArticle

Abstract

Aspergillus fumigatus is a filamentous fungus that can cause severe respiratory disease in immunocompromised individuals. A putative sialidase from A. fumigatus was recently cloned and shown to be relatively poor in cleaving N-acetylneuraminic acid (Neu5Ac) in comparison with bacterial sialidases. Here we present the first crystal structure of a fungal sialidase. When the apo structure was compared with bacterial sialidase structures, the active site of the Aspergillus enzyme suggested that Neu5Ac would be a poor substrate because of a smaller pocket that normally accommodates the acetamido group of Neu5Ac in sialidases. A sialic acid with a hydroxyl in place of an acetamido group is 2-keto-3-deoxynononic acid (KDN). We show that KDNis the preferred substrate for the A. fumigatus sialidase and that A. fumigatus can utilize KDN as a sole carbon source. A 1.45-Å resolution crystal structure of the enzyme in complex with KDN reveals KDN in the active site in a boat conformation and nearby a second binding site occupied by KDN in a chair conformation, suggesting that polyKDN may be a natural substrate. The enzyme is not inhibited by the sialidase transition state analog 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (Neu5Ac2en) but is inhibited by the related 2,3-didehydro-2,3-dideoxy-D-glycero- D-galacto-nonulosonic acid that we show bound to the enzyme in a 1.84-Å resolution crystal structure. Using a fluorinated KDN substrate, we present a 1.5-Å resolution structure of a covalently bound catalytic intermediate. The A. fumigatus sialidase is therefore a KDNase with a similar catalytic mechanism to Neu5Ac exosialidases, and this study represents the first structure of a KDNase.

Original languageEnglish (US)
Pages (from-to)10783-10792
Number of pages10
JournalJournal of Biological Chemistry
Volume286
Issue number12
DOIs
StatePublished - Mar 25 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of 'The Aspergillus fumigatus sialidase is a 3-deoxy-D-glycero-D-galacto-2- nonulosonic acid hydrolase (KDNase): Structural and mechanistic insights'. Together they form a unique fingerprint.

  • Cite this

    Telford, J. C., Yeung, J. H. F., Xu, G., Kiefel, M. J., Watts, A. G., Hader, S., Chan, J., Bennet, A. J., Moore, M. M., & Taylor, G. L. (2011). The Aspergillus fumigatus sialidase is a 3-deoxy-D-glycero-D-galacto-2- nonulosonic acid hydrolase (KDNase): Structural and mechanistic insights. Journal of Biological Chemistry, 286(12), 10783-10792. https://doi.org/10.1074/jbc.M110.207043