Heterologous expression of human N-acetyltransferases 1 and 2 and sulfotransferase 1A1 in Salmonella typhimurium for mutagenicity testing of heterocyclic amines

Food Chem Toxicol. 2002 Aug;40(8):1063-8. doi: 10.1016/s0278-6915(02)00032-7.


A variety of carcinogenic heterocylic amines (HAs) are found in cooked food. They can be metabolised to reactive intermediates via N-hydroxylation catalysed by cytochrome P450 1A2, followed by conjugation of the resulting N-hydroxyl group by N-acetyltransferase (NAT) or sulfotransferase (SULT). In order to compare the role of O-acetylation and O-sulfonation by human enzymes in the activation of HAs, we have introduced the cDNAs for wild-type forms of human NAT1, NAT2 and SULT1A1 in the acetyltransferase-deficient Salmonella typhimurium strain TA1538/1,8-DNP. Functional expression of recombinant proteins was demonstrated using immunoblot analysis and determination of enzyme activity with characteristic substrates. The established strains were used to study the mutagenicity of the N-hydroxy derivatives of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The results demonstrate that N-hydroxy-HAs are activated by different human enzymes. At the concentrations used in the mutagenicity assay, N-hydroxy-IQ was activated by human NAT2, but not by NAT1 or SULT1A1. In contrast, N-hydroxy-PhIP was activated specifically by human SULT1A1, but not by NAT1 or NAT2. Therefore, both O-acetylation and O-sulfonation by human enzymes have to be regarded as important determinants for HA genotoxicity in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyltransferases / genetics
  • Acetyltransferases / metabolism*
  • Amines / pharmacokinetics*
  • Arylamine N-Acetyltransferase / genetics
  • Arylamine N-Acetyltransferase / metabolism
  • Arylsulfotransferase*
  • Biotransformation
  • Gene Expression Regulation, Bacterial
  • Gene Expression Regulation, Enzymologic
  • Heterocyclic Compounds / pharmacokinetics
  • Humans
  • Imidazoles / metabolism
  • Immunoblotting
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Mutagenicity Tests
  • Mutagens / analysis*
  • Mutagens / metabolism
  • Quinolines / metabolism
  • Salmonella typhimurium / enzymology
  • Salmonella typhimurium / genetics*
  • Sulfotransferases / genetics
  • Sulfotransferases / metabolism*


  • Amines
  • Heterocyclic Compounds
  • Imidazoles
  • Isoenzymes
  • Mutagens
  • Quinolines
  • 2-amino-3-methylimidazo(4,5-f)quinoline
  • 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine
  • Acetyltransferases
  • Arylamine N-Acetyltransferase
  • N-acetyltransferase 1
  • NAT2 protein, human
  • Sulfotransferases
  • Arylsulfotransferase
  • SULT1A1 protein, human