[Substrate thermostabilization of soluble and immobilized glucoamylase].
A new kinetic approach to the study of enzyme thermal inactivation in the presence of a substrate, which influences the rate of inactivation has been developed. The method was applied to investigation of inactivation kinetics of soluble and porous silica-immobilized glucoamylase. It was found that the binding of a substrate (maltose or maltodextrines Star-Dri 24-R) increases the thermal stability of glucoamylase, the stabilizing effect being more pronounced in the case of the soluble enzyme (40-fold stabilization) as compared to the immobilized one (15-fold stabilization). The stabilizing effect does not depend on the length of the substrate (maltose, d. p. 2 or dextrines, d. p. 7). Glucose, a product of the enzymatic hydrolysis, has a much lower stabilizing effect. It was concluded that the main role in the glucoamylase thermostabilization is played by the substrate stabilization rather than by the immobilization itself (3-fold stabilization). However, a combined effect of thermostabilization of glucoamylase due to both immobilization and/or substrate stabilization is restricted by the same limit of value for immobilized and soluble enzymes, which is equal to 40--50-fold in comparison with the soluble enzyme in the absence of the substrate.
D001234:Aspergillus niger / Q000201:enzymology; D004355:Drug Stability; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005087:Glucan 1,4-alpha-Glucosidase / Q000378:metabolism*; D005959:Glucosidases / Q000378:metabolism*; D007700:Kinetics; D008320:Maltose; D008433:Mathematics; D012995:Solubility; D013696:Temperature
D004800:Enzymes, Immobilized; D008320:Maltose; D005959:Glucosidases; D005087:Glucan 1,4-alpha-Glucosidase
Termostabilizatsiia rastvorimoĭ i immobilizovannoĭ gliukoamilazy pod deistviem sybstrata.