A NEW SALMONELLA TESTER STRAIN EXPRESSING A HAMSTER ACETYLTRANSFERASE SHOWS HIGH-SENSITIVITY FOR ARYLAMINES

A hamster acetyltransferase, AT-I, has high activities for N-acetylation of arylamines, O-acetylation of N-hydroxyarylamines and N,O-acetyltransfer of N-hydroxyarylacetamides. In the present study, the cDNA was expressed in Salmonella typhimurium TA1538. The new SAT138 strain expressing high levels of AT-I showed remarkably high sensitivity (> 10,000 fold) for a carcinogenic intermediate, N-hydroxy-2-acetylaminofluorene, in an Ames mutagenesis test as compared to the parental TA1538 strain. SAT138 had 650-1,600-fold higher sensitivities for mutagenesis induced by 2-acetylaminofluorene and benzidine in the presence of S9 mix. Higher sensitivities (32-560-fold) were also observed with N-hydroxy-2-aminofluorene, N-hydroxy-4-aminobiphenyl, N-hydroxy-4-acetylaminobiphenyl, N-hydroxy-4-propionylaminobiphenyl and N-hydroxy-phenacetin in the absence of S9 mix. These high sensitivities to arylamines and the related chemicals are accounted for by the efficient expression of AT-I in the cytosol of this bacterium. The unique characteristics of SAT138 having high N-hydroxyarylacetamide N,O-transacetylating activity, which is defective in Salmonella acetyltransferase, provide broadened and high sensitivities for the detection of mutagenic N-substituted chemicals in the Salmonella mutagenesis test.