Hofmeister Effects in Enzymatic Activity:  Weak and Strong Electrolyte Influences on the Activity of Candida rugosa Lipase

Abstract

The effects of weak and strong electrolytes on the enzymatic activity of Candida rugosa lipase are explored. Weak electrolytes, used as buffers, set the pH, while strong electrolytes regulate the ionic strength. The interplay between pH and ionic strength has been assumed to be the determinant of enzymatic activity. In experiments that probe activities by varying these parameters, there has been little attention focused on the role of specific electrolyte effects. Here we show that both buffers and the choice of background electrolyte ion strongly affect the enzymatic activity of Candida rugosa lipase. The effects here shown are dramatic at high salt concentration; indeed, a 2 M concentration of NaSCN is able to fully inactivate the lipase. By contrast, Na2SO4 acts generally as an activator, whereas NaCl shows a quasi-neutral behavior. Such specific ion effects are well-known and are classified among the "Hofmeister effects". However, there has been little awareness of them, or of their potential for optimization of activities in the enzyme community. Rather than the effects per se, the focus here is on their origin. New insights into mechanism are proposed.

Impact of electric field on Hofmeister effects in aggregation of negatively charged colloidal minerals

“…34 Fortunately, several recent studies [33][34][35] have disclosed the essential role of polarization effect played in Hofmeister effects at interface surfaces, and these results provided motivation for us. Furthermore, some investigations 8,29,32 along with the present work pointed out that quite a different Hofmeister series were observed at relatively low and high ionic concentration. Usually, the reversal or partial alteration of Hofmeister series are relevant to change of the nature of the particle surface, including the cationic or anionic character 3,28,36,37 and the hydrophobic/hydrophilic character of the particle surface.…”

“…3 Following pioneering experiments conducted on the capacity of * For correspondence ions to stabilize protein solutions against precipitation by Franz Hofmeister in the late 19 th century, it was clear that aggregation and sedimentation of proteins in electrolyte solutions vary remarkably with ionic species, even if the valence and chemical nature of these ions are similar. 4 Over the last decades, Hofmeister effects have been observed ubiquitously in colloidal, nanocrystal and biological systems, including bacteria growth, 5,6 enzyme activity, [7][8][9] colloidal stability, 3,10 cation exchange equilibrium 11 and mineral dissolution. 12 These effects can influence the interactions of ions with different interfaces (metal/water, air/water, oil/water and water/solid), 13,14 as well as affect the physicochemical properties of the solution or colloids, such as activity coefficient, Zeta potential, freezing point, osmotic pressure, photoluminescence and catalytic properties.…”

Specific ion effects on the electrochemical properties of cytochrome c

“…Such effects were first described by Hofmeister who observed that the nature of the salt used affected 20 the solubility of egg-white proteins in aqueous solutions. 15 The efficiency of salts in promoting protein precipitation was found to be:…”

“…The effect of cations can not be explained by this rule. However, both anion and cation effects can be understood by taking into account the 20 cooperative action of electrostatic and ion dispersion forces. The results demonstrate that the choice of supporting electrolyte in electrochemical investigations of redox proteins is important and emphasize that care needs to be taken in the determination and comparison of E°', H o' and S o' in different solutions.…”

Effect of Properties of Phosphate Buffer Saline Solutions on Vibrational Characteristics of a Quartz Crystal Microbalance Resonator

“…It has been widely reported that buffers not only control pH, but also have specific effects on protein activity, such as enzymatic catalysis, (2,3) protein conformational stability, (4) bioreactivity, (5)(6)(7)(8) and protein thermal events. (9) The selection and optimization of buffer solutions are important issues to maintain proper bioactivity; typical factors include buffer type, buffer concentration, and identity of added salt and its concentration as described in the cited references.…”