Improved refolding of denatured/reduced lysozyme using disulfide-carrying polymeric microspheres

Many proteins tend to aggregate during refolding, especially at high protein concentrations. To reduce aggregation and improve the refolding yields, denatured/reduced lysozyme at 0.5 mg ml(-1) was refolded using disulfide-carrying microspheres. The extent of renaturation was evaluated by measuring the content of recovered soluble protein and its enzymatic activity. Addition of the dispersion of the modified microspheres to the aqueous solution of reduced lysozyme resulted in the binding of the proteins on the microsphere surface, followed by the spontaneous release of the bound proteins. As a consequence, a 10% active enzyme was obtained. However, no renaturation occurred without the microspheres due to aggregation. Moreover, when glutathione was added 20 h after incubation with the microspheres, the refolding yields could increase to approximate to 40%. These results indicate that the disulfide moieties of the microspheres play an important role in preventing the aggregation process and catalyzing the refolding reaction through the thiol-disulfide interchange reactions. (C) 2000 Elsevier Science B.V. All rights reserved.