Determination of the pH-dependent immobilization efficacy of α-glycosidase and its catalytic performance on SnO2:Sb/ITO thin films

Abstract

Non-toxic antimony coated tin oxide (SnO2:Sb/ITO) thin films were prepared to obtain immobilized α-glycosidase (i-α-glycosidase) with better in-vitro activity and storage stability, considering its possible use in future studies on effective anti-diabetic drugs and inhibition. The optimum pH value was determined to be 7.5 via electrostatic surface potential map studies for high activity and immobilization efficiency. An increase in the affinity of α-glycosidase to p-Nitrophenyl-α-glucopyranoside substrate was shown with the change of negative binding energy from -7.1 to -7.3 kcal/mol. The activity values of free-α-glycosidase and i-α-glycosidase were determined at 400 nm by UV–vis spectrophotometric method. The residual activity of i-α-glycosidase after one week was obtained 73.22 % for pH 7.5. The catalytic residues of α-glycosidase were identified as Trp391, Gly566, Asp568, and Trp710 for the best polar contacts with the substrate. The best relative activity and specific activity (U/mg) values at all pH values were obtained in the immobilized enzyme form. High immobilization efficiency was obtained with a value of 85.71 % for pH 7.5. Fourier transform infrared (FTIR) spectrophotometer bandgap values and scanning electron microscopy (SEM) studies proved that α-glycosidase immobilization was successfully performed. As a result, we conclude that SnO2:Sb/ITO thin films could be suitable immobilization materials and therefore may prove beneficial for various biotechnological, pharmacological, and therapeutic applications alike.