Characterization and stability of D-amino acid oxidase and catalase within the permeabilized recombinant Pichia pastoris cells

An effort was devoted to the detailed characterization and stability analysis of d-amino acid oxidase (DAAO) and catalase (CAT) in the permeabilized cells, involved in a summary of our previous works. It was observed that the culture conditions, the permeabilization treatments, the enzyme leakage and pH value of solution except the enzyme expression levels, displayed a significant effect on the enzyme stability. About 96% of the CAT activity in the cetyltrimethylammonium bromide (CTAB)-permeabilizied cells was inhibited when treated with sodium azide (0.8 M, 30 min), while no visible effect on the activity and stability of DAAO was detected. Though, almost 100% of the CAT activity in the CTAB-permeabilized cells could be eliminated by the alkali treatment (pH 11.5, 30 min), both the activity and stability of DAAO were slightly impaired. The half-life of DAAO could be up to 15.5 days by treating the CTAB-permeabilized cells with 1% glutaraldehyde (GLA). Additionally, it was noted that the gene sources and expression hosts might play an important role on the stability of DAAO and CAT in permeabilized cells.