Preparation of immobilized enzyme with high activity using affinity tag based on proteins A and G

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Abstract
Affinity tag AG consisting of immunoglobulin G (lgG)‐binding domains of protein A from Staphylococcus aureus (EDABC) and those of protein G from Streptococcus strain G148 (C2C3) were used to facilitate immobilization of β‐galactosidase (βgal) from Escherichia coli. Poly(methylmethacrylate/N‐isopropylacrylamide/methacrylic acid) [P(MMA/NIPAM/MAA)] and poly(styrene/N‐isopropylacrylamide/methacrylic acid) [P(St/NIPAM/MAA)] latex particles, which show thermosensitivity, were used as support materals to prepare affinity adsorbents. Human γ‐globulin (HγGb), whose major fraction is lgG, was used as an affinity ligand and was covalently immobilized onto the both latex particles by the carbodiimide method under various conditions. A fusion protein, AGβgal, was immobilized at pH 7.3 by the specific binding of affinity tag to these affinity adsorbents. The amount of adsorbed AGβgal per unit amount of immobilized HγGb, namely, efficiency of ligand utilization, was strongly affected by the type of latex particles and pH value for HγGb immobilization. The efficiency of ligand utilization was maximum in the affinity adsorbents prepared at pH 6.0 to 7.0, and that in the HγGb–P(MMA/NIPAM/MAA) latex particles was high. This result could be explained by the conformation and orientation of immobilized HγGb molecules. Immobilized AGβgal retained approximately 75% of its activity in solution and the binding is stable enough to allow repeated use. These results clearly demonstrate that combination of the affinity tag AG and the affinity adsorbents, based on the thermosensitive latex particles, offers a simple and widely applicable method for preparation of immobilized enzyme with high activity. © 1995 John Wiley & Sons, Inc.