Influenza virus sialidase: effect of calcium on steady-state kinetic parameters

Biochim Biophys Acta. 1991 Mar 8;1077(1):65-71. doi: 10.1016/0167-4838(91)90526-6.

Abstract

Ca2+ increases the initial rate of activity of sialidase from influenza virus (A/Tokyo/3/67). Increasing ionic strength also activates influenza virus sialidase. When ionic strength is controlled, smaller but still significant Ca2+ effects are observed, with Vmax/Km increased from 0.8.10(5) to 1.4.10(5) M-1 s-1 and Vmax increased from 6.3 to 9.5 s-1 by saturating Ca2+. The Ki of the competitive inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid was decreased from 2.7.10(-6) to 1.15.10(-6) M after the addition of saturating Ca2+. The data show that Ca2+ exerts a specific effect on Vmax/Km, leading to an increased rate of interaction of substrate with the enzyme. The Kd-app for the Ca2(+)-sialidase complex is 2 mM. Except for Mg2+ which behaves similarly to Ca2+, other mono- and divalent cations have little specific effect on sialidase kinetics. Sequence analysis of a range of subtypes of sialidases from influenza virus supports the proposal that Ca2+ binds at the subunit interface transmitting a conformational change to the enzyme active site. Ca2+ activation may have a physiological role in switching on sialidase activity during the release of newly synthesised virions from the host cell surface.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Binding, Competitive
  • Calcium / pharmacology*
  • Influenza A virus / enzymology*
  • Kinetics
  • Mathematics
  • Models, Molecular
  • Molecular Sequence Data
  • Neuraminidase / metabolism*
  • Osmolar Concentration
  • Protein Conformation

Substances

  • Neuraminidase
  • Calcium