Temperature Induced Conformational Entropy of α-Amylase with and without Additive

Aims: 1) To formulate models based on defined principle for the application of Fitter’s model and 2) ultimately show that there are changes in the radius of an enzyme in solution and consequently conformational entropy change with temperature before and during catalytic activity.

Study Design: Theoretical and experimental.

Place and Duration of Study: Department of Chemistry and Biochemistry, Research Division, Ude International Concepts LTD (862217), B. B. Agbor, Delta State, Nigeria; Owa Alizomor Secondary School, Owa Alizomor, Ika North East, Delta State, Nigeria. The research was conducted between June and December, 2016.

Methodology: Bernfeld method of enzyme assay was used. Assays were carried out on diluted crude human salivary alpha amylase (HSaA). Data from assay were plotted in two ways viz: Velocity (v) vs thermodynamic temperature (T) and 1/v vs T. Proportionality constants were determined from slope and intercept of the linear regression. These were used to determine desired parameters.

Results: The results showed that, hydrodynamic radius, rp0 (or positive Dr) was higher at higher temperatures and in the absence of calcium salt. Without calcium chloride but with raw starch and gelatinized starch, Dr values were in the range of 0.81 Å-2.30 Å and 4.5 Å-8.45 Å respectively. With calcium chloride and gelatinized starch at higher temperatures, Dr ranged from 3.71 Å-4.80 Å. Increasing values of rp0 corresponded with increasing values of conformational entropy change, DSconf.

Conclusion: The derived models were theoretically/conceptually and experimentally compatible given that the hydrodynamic radius, rp0 (or positive Dr) increased with the increase in temperature whether or not the enzyme showed increasing activity. The activity of the enzyme decreases when physiological limit of DSconf is exceeded. The values of Dr were higher at higher temperatures in the presence and absence of calcium chloride.