Lineweaver Burk Plot, Rate Constant, and Mathematical Relationship between Molar Mass and Free Energy of Activation: “To be or not to be”

Aims: Verify a derived kinetic parameter dependent model for the determination of Gibbs free energy of activation and consequently rate constant and to show that despite criticism against the process, Lineweaver Burk plot and the rate constant, both process and term remain indispensible for the determination of Gibbs free energy of activation for a nonstandard solution of an enzyme in particular.

Study Design: Experimental investigation involving in vitro assay of Aspergillus orzyzea alpha amylase using gelatinized soluble potato starch for test backed with control test without substrate as the blank.

Place and Duration of Study: Research Division of Ude Concept International Limited (RC: 862217), B. B. Agbor, Delta State, Nigeria. The investigation lasted for one year as part of a series of research between 2013 and 2016.

Methodology: Bernfeld method of enzyme assay was used. Controls were free from substrate.

Results: The result of investigation showed that Gibbs free energy (△Ga) values were 59.20±0.11 kJ/mol (from old model; n = 6) and 59.43±0.19 kJ/mol (from new model; n = 2) while rate constant (k2) was 10385.08±55.13/min (n = 2) at pH, 5 and temperature, 20°C; The △Ga values, 57.50±0.29 kJ/mol (from old model; n = 6), 57.82±0.04 kJ/mol (from new model; n = 5), and 57.58±0.16 (from old model; n = 5) and k2values, 23536.77±3045.794/min(n = 6) and 20210.95±1344.04/min (n = 5) were reported at pH 6.9 and 21°C.

Conclusion: The Gibbs free energy (△Ga) and rate constant (k2) values calculated using the old and new models were similar. The derived model which suggested that △Ga α In (1/MPROT)2 at a given temperature stands verified. Thus the continuous use of Lineweaver Burk plot and the kinetic parameter, k2 as defined remains very necessary due to vital and useful results obtainable when they are used.