Study on Arsenic Methyltransferase Expressed in Recombinant E. coli

This study aimed to facilitate efficient arsenic detoxification by inducing the microbial methylation of inorganic arsenic. Recombinant Escherichia coli strains K63 and KC42 were transformed to overexpress arsenic methyltransferase, and the methylation of inorganic arsenic was evaluated using the enzyme extracted from these strains. To ensure continuous reactions by maintaining enzymatic activity, the extracted enzyme was immobilized in microcapsules (MC) to catalyze the methylation of inorganic arsenic. The total yield of methylated organic arsenic compounds in strain K63 was 32.9% (after 2 h of incubation at pH 7.0 and 35°C), of which trimethyl arsenic compounds (TMAC) accounted for 8.3%. The total yield in strain KC42 was 35.9% (after 2 h of incubation at pH 6.5 and 35°C), of which TMAC accounted for 10.8%. When arsenic was methylated using MC prepared with the crude enzyme solution, the total yield of methylated organic arsenic compounds was 12.6% and 5.7% in strains K63 and KC42, respectively. The residual enzymatic activity was calculated to be 53.1% and 48.8% in strains K63 and KC42, respectively. Future studies should aim to increase the residual enzymatic activity, thus elevating the yield of organic arsenic compounds, by optimizing the conditions for enzyme immobilization in MCs.