BIOACTIVATION OF AROMATIC-AMINES BY RECOMBINANT HUMAN CYTOCHROME P45011A2 EXPRESSED IN AMES TESTER STRAIN BACTERIA - A SUBSTITUTE FOR ACTIVATION BY MAMMALIAN TISSUE PREPARATIONS

The most widely used bioassay in genetic toxicology is the Ames test, which combines a bacterial mutagenicity assay (reversion of Salmonella typhinurium histidine-auxotrophic tester strains) with an exogenous b ioactivation system (hepatic postmitochondrial supernatant or ''S9''). The enzymatic activities of S9 prepared from the tissues of experimen tal animals are difficult to control. We show that the requirement for S9 can be obviated by the engineered expression of enzymes of bioacti vation within the bacterial cell. With this strategy, reactive metabol ites are produced inside the bacterial cell, proximate to the genetic target. Species boundaries can be crossed, and chimeric or mutant enzy mes can be studied. We have constructed an Ames tester strain, express ing both aromatic amine N-acetyltransferase and human cytochrome P4501 A2, which detects aromatic amine mutagenicity in the absence of S9.