Calcium Chloride Can Influence the Stability Flexibility Complementarity and Consequently, Activity of Hydrolases: A Case Study on Porcine Alpha Amylase

Aims: The specific aims of the research were i) to investigate the effects of extra “load” of calcium chloride at different temperatures and ethanol on the specific activity of porcine alpha amylase (PPA), ii) characterize the effect of extra calcium chloride in terms of thermodynamic and activation parameters, and iii) determine the (un) folding cooperativity (m – value) as well as free energy of folding – unfolding transition.

Study Design: Experimental.

Place and Duration of Study: Research Division of Ude Concept International Limited (RC 862217), B. B. Agbor, Delta State, Nigeria and Ambrose Alli University Ekpoma, Nigeria. This study is part of a series of research that lasted for 7 months.

Methodology: Bernfeld method of enzyme assay was used. Controls were free from additives while the experimental test was either with calcium chloride or a mixture of alcohol and calcium chloride.

Results: The results presented graphically and in the Tables showed that the specific activity and kinetic parameters of the enzyme with Ca2+ - salt were higher than without Ca2+ - salt. The activation parameters, free energy (DG#), enthalpy (DH#), and entropy(DS#) for Ca2+ - salt treated enzyme were 77.36±0.11 kJ/mol, 54.95±0.96 kJ/mol, and - 68.39±3.03 J/mol.K respectively at 318.15 K. The enthalpy (DH) of enzyme substrate (ES) formation was - 41.10 for Ca2+ - salt treated enzyme. The m – values were positive in sign in the presence of Ca2+ - salt with all alcohols except local gin. All free energy values for folding – unfolding transition at infinite dilution of the Ca2+ - salt were negative for all alcohols except with local gin.

Conclusion: The presence of extra Ca2+ - salt can increase the specific activity, rate constant and catalytic efficiency of the enzyme. The ground state of Ca2+-salt treated enzyme is less flexible than Ca2+-salt free enzyme. The hydrolysis of starch is enthalpically driven in the presence of Ca2+-salt, while entropic factor is the case in the absence of the salt. The positive m – values implied that Ca2+- salt can oppose the effect of a chaotrope like ethanol on the enzyme.