Abstract
Polymethylglutamate (PMG), a synthetic polypeptide, was used as a carrier to immobilize glucose oxidase (EC 1. 1. 3. 4), uricase (EC 1. 7. 3. 3), peroxidase (EC 1. 11. 1. 7), trypsin (EC 3. 4. 21. 4), chymotrypsin (EC 3. 4. 21. 1), urease (EC 3. 5. 1. 5), and aminoacylase (EC 3. 5. 1. 14) by the azide method. The enzymes could be immobilized covalently on PMG coated on glass beads. The retained activities of all the immobilized enzymes were excellent (more than 90%). The amount of enzyme immobilized on the polymer varied markedly depending on the kind of enzyme (trypsin 30 mg, chymotrypsin 27 mg, urease 5.8 mg, uricase 5.6 mg, aminoacylase 2.3 mg, glucose oxidase 1.8 mg and peroxidase 2.3 mg/100 mg PMG). It was found that the amount of bound enzyme was determined primarily by the molecular weight and secondarily by the content of lysine residues in the enzyme. The heat stabilities of the resulting immobilized enzymes were markedly improved, while the optimal pH and Km values were almost unchanged. The enzymes immobilized on PMG showed improved stability because of both the increased hydrophilicity of the polymer and the multipoint binding mode, including covalent and ionic bonding.
