Characterisation of an ionisable group involved in binding and catalysis by sialidase from influenza virus
Chong, A.K.; Pegg, M.S.; von Itzstein, M.
Biochemistry International 24(1): 165-171
1991
ISSN/ISBN: 0158-5231 PMID: 1768256 Document Number: 628
The effect of pH on the kinetics of sialidase purified from influenza virus (A/Tokyo/3/67, H2N2) was investigated. A pK of 9.0 for inhibition of the enzyme by three competitive inhibitors, due to an ionisable group in the active site, was observed. A similar pK was observed for V/Km for the fluorogenic substrate 2-(4-methylumbelliferyl)-N-acetyl-.alpha.-D-neuraminic acid. However, the shape of the V/Km profile indicates that this substrate is sticky. Solvent perturbation experiments indicated that the observed ionisable active site group is likely to be a cationic amino acid. The results provide evidence against the hypothesis that Glu 276 acts as a proton donor in the enzyme reaction and supports the proposal of a role for one of the active site cationic amino acids in binding and catalysis.
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