Abstract In order to obtain active Arabidopsis thaliana alpha-dioxygenase 2 (AtDOX2), the encoding sequence of AtDOX2 was cloned into pPIC9k to obtain pPIC9k-AtDOX2. The recombinant vector was linearized and electrophorated into Pichia pastoris strain GS115. After G418 selection, PCR analysis and optimization of methanol inducing time，the high level expression strain of GS115/pPIC9k-AtDOX2 was obtained. SDS-PAGE analysis revealed that the expression level of recombinant protein reached to top at 96 h after inducing by 0.5% methanol and the target protein accounted for 15% of the extracellular total protein. The 70 kD recombinant AtDOX2 was purified by the Ni-NTA chromatography column, and the purity of recombinant protein was more than 80%. The peroxidase activity of the purified protein was tested by the 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) assay, the result showed that the recombinant protein had peroxidase activity, and the peroxidase activity of AtDOX2 could be activated by Ca2+ and Mg2+ and inhibited by EDTA, imidazole and Mn2+. The α-dioxygenase activity was analyzed by 2,4-dinitrophenyl hydraz(2, 4-DNP) assay, the result showed that the recombinant protein had dioxygenase activity, and the α-dioxygenase activity of AtDOX2 could be activated by Ca2+ too. Results indicate that the ecombinant AtDOX2 was expressed and purified by yeast system, and it acts as a dual functional enzyme of peroxidase and dioxygenase.
