Aims: 

Aluminium does not belong to essential elements, and as a non-regulatory ion can be toxic to many organisms. Average daily dietary aluminium intake is approximately 2-6 mg Al/day in children and 6-14 mg Al/day in adults. An additional source of aluminium is food additives and Al-containing antacids. The purpose of this study was the investigation of the in vitro effect of Al³⁺ ions in strong acid conditions on pepsin (E.C.3.4.23.1.) activity and its electrophoretic mobility.

Methods: 

The Worthington method based on enzyme-catalyzed measured rate of hydrolysis of denatured haemoglobin substrate was used for evaluation of enzyme activity in the absence (control) and presence of Al³⁺ ions. Kinetic analysis was carried out according to a slightly modified method of Anson. The data analyzed by the software package Origin 6.1 and the results were recalculated using EZ FIT. Native electrophoresis of pepsin on 10% polyacrylamide gel carried out at 4°C according to the Laemmli procedure.

Results: 

It was demonstrated that Al³⁺ ions stimulate the pepsin activity on concentration dependent manner. Kinetic analysis showed that Al³⁺ ion (10^-2– 10^-6 M) increases the maximal velocity (V_max) rather than the apparent activity (K_m) implying the noncompetitive nature of activation. Native PAGE electrophoresis shows the decrease in electrophoretic mobility of pepsin which is proportional to the concentrations of Al³⁺ ions.

Conclusion: 

The present kinetic analyses indicated that the activation by Al³⁺ ions was of partial non-competitive type, which classifies this phenomenon as a case of non-essential activation. The decrease in the electrophoretic mobility of pepsin molecule additionally confirms the conformational changes in pepsin induced by Al³⁺ binding.