title: Properties of Rhodotorula gracilis D-amino acid oxidase immobilized on magnetic beads through his-tag.
abstract: D-amino acid oxidase catalyzes one of the key steps in the production of semisynthetic cephalosporins. We expressed and purified recombinant Rhodotorula gracilis D-amino acid oxidase with C-terminal his-tags. This engineered enzyme was immobilized onto Ni(2+)-chelated nitrilotriacetic acid magnetic beads through the interaction between his-tag and Ni(2+). The kinetic constants, storage properties, and the reusability of the immobilized d-amino acid oxidase were determined. The effects of temperature, pH, and hydrogen peroxide on the activity of immobilized d-amino acid oxidase were also studied. The highest activity recovery was 75%. Thermal stability was improved after immobilization; the relative activity of the immobilized enzyme was 56% whereas the free enzyme was completely inactivated after incubation at 50 degrees C for 1 h. In the presence of 10 mM hydrogen peroxide, the immobilized enzyme did not show a rapid loss of activity during the first 2 h of incubation, which was observed in the case of the free enzyme; the residual activity of the immobilized enzyme after 9 h was 72% compared with 22% of the free form. The long-term storage stability was improved; the residual activity of the immobilized enzyme was 74% compared with 20% of the free enzyme when stored at room temperature for 10 d. The immobilized form retained 37% of its initial activity after 20 consecutive reaction cycles.
authors.affiliation: Department of Bioengineering, Tatung University, 40 Chungshan N. Rd. Sec. 3, Taipei 10452, Taiwan.
authors.forename: Iching
authors.initials: I
authors.lastname: Kuan
authors.forename: Renjie
authors.initials: R
authors.lastname: Liao
authors.forename: Haochieh
authors.initials: H
authors.lastname: Hsieh
authors.forename: Kuanchun
authors.initials: K
authors.lastname: Chen
authors.forename: Chiyang
authors.initials: C
authors.lastname: Yu
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003605:D-Amino-Acid Oxidase / Q000737:chemistry*; D004789:Enzyme Activation; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry; D006639:Histidine / Q000737:chemistry*; D008280:Magnetics; D008863:Microspheres; D011485:Protein Binding; D012248:Rhodotorula / Q000201:enzymology*
chemical_list: D020099:Coated Materials, Biocompatible; D004800:Enzymes, Immobilized; D006639:Histidine; D003605:D-Amino-Acid Oxidase