Formation of 2‐Amino‐3‐methylimidazo[4,5‐f]quinoline‐ and 2‐Amino‐3,8‐dimethylimidazo[4,5‐f]quinoxaline‐sulfamates by cDNA‐expressed Mammalian Phenol Sulfotransferases

In rat liver cytosol systems, 2‐amino‐3‐methylimidazo[4,5‐f]quinoIine (IQ) and 2‐amino‐3,8‐dimethyl‐imidazo[4,5‐f]quinoxaline (MelQx) were converted into their sulfamates in the presence of 3′‐phosphoadenosine 5′‐phosphosulfate at rates of 51.2 and 50.7 pmol/min/mg cytosol in the male, and 23.7 and 22.5 pmol/min/mg cytosol in the female, respectively. IQ‐sulfamate formation was low (0.24 pmol/min/mg cytosol) in human liver cytosols, and MeIQx‐sulfamate was not detected (<0.1 pmol/ min/mg cytosol). These results suggest only a minor contribution of IQ‐ and MeIQx‐sulfamate formation to the detoxification of both heterocyclic amines in humans. Using sulfotransferase cDNA‐expression systems, a rat ST1A1 arylsulfotransferase has been shown to catalyze the formation of the sulfamates, suggesting a role of the ST1A type of sulfotransferase in the N‐sulfation of heterocyclic amines.