Immobilization of native and poly(ethylene glycol)-treated ('PEGylated') bovine serum amine oxidase into a biocompatible hydrogel.

Abstract

Native bovine serum amine oxidase (BSAO) and poly(ethylene glycol) (PEG)-treated ('PEGylated') BSAO were immobilized into a hydrogel during its synthesis. The hydrogel was obtained by cross-linking of BSA with PEG di-nitrophenyl carbonates with a molecular mass of 10 kDa. Approx. 60% of the amino groups at the surface of BSAO were modified by monomethoxy-PEG with a molecular mass of 5 kDa when the reaction was carried out for 5 h in borate buffer, pH 9. The number of anchorage points of BSAO in the matrix, which was determined as minimal when PEGylated BSAO was used or maximal when native BSAO was used, did not influence the apparent K(m) and V(max) values of the different preparations. The apparent K(m) values of both forms of the enzyme were decreased due to preconcentration of benzylamine substrate by the negatively charged hydrogel. V(max) values were generally lower upon immobilization. We can therefore conclude that the hydrogel swelling has no significant effect on the enzyme's structure. The operational stability, evaluated in the presence of substrate, was generally increased upon enzyme immobilization into the hydrogel. Enzymic hydrogels were very stable during storage in solution at 4 degrees C, maintaining a high activity even after several weeks. The immobilization of both forms of BSAO did not improve their thermostability at 65 degrees C. The BSA-PEG hydrogel is a good matrix for immobilization of enzymes with therapeutic potential such as BSAO.