Abstract:The gene coding triphenylmethane dyes degradation enzyme (TpmD) was amplified from genomic DNA of Aeromonas hydrophila strain DN322 by PCR and cloned into the expression vector pET22b (+). After being confirmed by sequencing, the recombinant vector pET22-tpmD was transformed into Escherichia coli BL21(DE3), and then a clone with high yeild of TpmD was screened. The expression of TpmD was induced with IPTG and the specific activity of TpmD from pET22-tpmD/BL21 (DE3)’s cell-free extract, were 569.5,386.9,516.1 and 273.0U/g with crystal violet, malachite green, fuchsin basic and brilliant green as substrates, respectively. After one step purification by Ni-NTA agarose column, the specific activities of TpmD were increased to 1075.3, 1042.8, 903.9 and 484.3U/g, the purity of this enzyme reached up to 94.05%. The stability of the recombinant plasmid makes it easy to produce the protein on a large scale fermention.