D-Amino acid oxidases from Rhodosporidium toruloides and Trigonopsis variabilis (RtDAO and TvDAO) are both yeast homodimeric flavoenzymes. Two of their cDNA genes were connected by a hexanucleotide linker and heterologously expressed in E. coli to produce the corresponding double DAOs (dRtDAO and dTvDAO) with two subunits fused into a single polypeptide. The specific activities of double DAOs remained similar to those of native dimeric DAOs, although the catalytic efficiencies (kcat/KM) were decreased due to higher KM values. The Tm value for dRtDAO was shifted 5°C higher while that for dTvDAO was increased only by 2°C, in comparison with the corresponding native counterparts. In the presence of 10 mM H2O2, dRtDAO and dTvDAO exhibited half-lives of about 60 and 40 min, respectively, which were 2- and 1.5-fold, respectively, longer than their native DAOs. These yeast DAOs can therefore be thermally and oxidatively stabilized by linking their subunits together.