STUDIES ON THE THERMAL INACTIVATION OF IMMOBILIZED ENZYMES

The thermal inactivation of a great number of immobilized enzymes shows a biphasic kinetics, which distinctly differs from the first-order inactivation kinetics of the corresponding soluble enzymes. To interpret the mathematical model function, the catalytic properties of immobilized enzymes (number of active sites in silica-bound trypsin, K//M and E//a values in silica-bound alpha -amylase and chymotrypsin) at different stages of inactivation and the influence of various factors (coupling conditions, addition of denaturants or stabilizers, etc. ) on the thermal inactivation of silica-bound alpha -amylase were studied. Furthermore, conformational alternations in the thermal denaturation of spin-labeled soluble and silica-bound beta -amylase were compared by electron spin resonance (ESR) studies. The results suggest that the biphasic inactivation kinetics reflects two different pathways according to which catalytically identical enzyme molecules are predominantly inactivated.