title: Mechanism of thermoinactivation of immobilized glucose isomerase.
abstract: Irreversible thermoinactivation of immobilized glucose isomerase from Streptomyces olivochromogenes has been mechanistically investigated at the pH-optimum of enzymatic activity (pH 8.0). Ligands (high fructose corn syrup and the competitive inhibitor xylitol) greatly stabilize the immobilized enzyme at high temperatures. At 90 degrees C in the presence of 2M xylitol, irreversible inactivation of immobilized glucose isomerase is caused by deamidation of its asparagine/glutamine residues. On the basis of the data obtained, it appears that the time-dependent decay of glucose isomerase activity in industrial bioreactors is brought about by oxidation of the enzyme's cysteine residue and/or heat-induced deleterious reactions with high fructose corn syrup or its impurities.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Volkin
authors.forename: A M
authors.initials: AM
authors.lastname: Klibanov