Irreversible thermal inactivation and conformational lock of alpha glucosidase

Abstract

In the present work, we studied the structure-activity relationship and kinetics of thermal inactivation of �-glucosidase A (AglA) in a 50 mM potassium phosphate buffer at pH 6.8 using p-nitrophenyl �-d-glucopyranoside (pNPG) as the synthetic substrate following absorbance at 410 nm by UV?Vis spectrophotometer. The interface structure and residual activity plot were analyzed via biochemical measurements by means of conformational lock theory, as well. The thermal inactivation curves were plotted in temperature interval from 30 to 50 �C. Based on experimental and structural data we suggested intermediates during inactivation before the loss of enzyme activity. Arrhenius plot for thermal inactivation rate constant showed biphasic appearance related to before and after 45�C temperature. The contact areas between two subunits were ruptured and unlocked stepwise during dimer dissociation. Cleavage of these areas induced the dissociation of the subunits along with destruction of the active centers and subsequently the loss of activity. It seems that the contact areas interact with active centers by conformational changes involving secondary structural elements.