Catalysis of protein folding by agarose-immobilized protein disulfide isomerase.

Protein disulfide isomerase (PDI) catalyzes the formation and rearrangement of disulfide bonds during protein folding. PDI coupled to cyanogen bromide-activated agarose retains its catalytic activity, and a column of this material increases both the rate and the yield for folding disulfide-containing proteins. For reduced, denatured ribonuclease, the overall yield of fully active ribonuclease isolated from the PDI column in one pass was 85-98% of the applied protein. Under the same conditions in the absence of PDI, ribonuclease regained only 16% of its native activity. The oxidative folding of reduced denatured lysozyme is complicated by aggregation so that in the absence of PDI optimal yields of only < or = 25% are obtained at lysozyme concentrations of 1.6 mg/ml. When reduced, denatured lysozyme (1.6 mg/ml) is passed over a PDI column in 1-2 M urea in the presence of a glutathione redox buffer, the specific activity of the recovered lysozyme is identical to that of the native enzyme and the total recovery of the applied protein is 50-65%.