Picture of a black hole

Strathclyde Open Access research that creates ripples...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of research papers by University of Strathclyde researchers, including by Strathclyde physicists involved in observing gravitational waves and black hole mergers as part of the Laser Interferometer Gravitational-Wave Observatory (LIGO) - but also other internationally significant research from the Department of Physics. Discover why Strathclyde's physics research is making ripples...

Strathprints also exposes world leading research from the Faculties of Science, Engineering, Humanities & Social Sciences, and from the Strathclyde Business School.

Discover more...

Hofmeister effects on activity and stability of alkaline phosphatase

Yang, Z. and Halling, P.J. (2010) Hofmeister effects on activity and stability of alkaline phosphatase. BBA - Biomembranes, 1804 (4). pp. 821-828. ISSN 0005-2736

[img] Microsoft Word (Yang10BBA_preprint.doc)
Yang10BBA_preprint.doc

Download (1MB)

Abstract

We have studied the effects on alkaline phosphatase of adding high concentrations (normally 1.0 M) of simple salts. It is necessary to allow for significant effects of salts on the extinction coefficient of the reaction product, and on the apparent pH of the buffer. Both activity and stability of the enzyme correlate well with the Hofmeister series in terms of the salt's kosmotropic/chaotropic properties, which are assessed by the Jones-Dole viscosity B coefficients (B+ for cations and B_ for anions). The catalytic activity or V-max/K-m of the enzyme showed a bell-shaped relationship with the (B_ -B+) values of the salts present, being optimal with salts (such as NaCl, KCl, and KNO3) where the anion and cation have similar kosmotropic/chaotropic properties. This effect is believed to be enzyme-specific and relates to the impact of both cations and anions on the enzyme's surface pH, active site, and catalytic mechanism. Anions play a more predominant role than cations in affecting enzyme stability. The rate of irreversible thermal inactivation is strongly reduced by addition of kosmotropic anions like SO42- (half-life increased from 8 to 580 min at 60 degrees C). This effect is general and the mechanism probably involves the ability of the ions to affect the water solvation layer around the enzyme molecule and to interact with both the surface and internal structure of the enzyme.