Arylamine N-acetyltransferases: covalent modification and inactivation of hamster NAT1 by bromoacetamido derivatives of aniline and 2-aminofluorene |
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Authors: | Guo Zhijun Vath Gregory M Wagner Carston R Hanna Patrick E |
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Institution: | Department of Medicinal Chemistry, University of Minnesota, 308 Harvard St. S.E., Minneapolis, MN 55455, USA. |
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Abstract: | Kinetic analysis of the inactiviation of hamster NAT1 by 2-(bromoacetylamino)fluorene (Br-AAF) and bromoacetanilide revealed that Br-AAF is an active site directed affinity label whereas bromoacetanilide acts as a bimolecular alkylating agent. ESI MS analysis of NAT1 treated with Br-AAF showed that a single molecule of 2-acetylaminofluorene had been incorporated. Proteolysis with pepsin followed by sequencing of adducted peptides by ESI MS/MS identified the modified residue as the catalytically essential Cys-68. ESI Q-TOF MS analysis of NAT1 that had been treated with bromoacetanilide resulted in identification of a monoadducted protein as the primary product and a diadducted protein as a minor product. Pepsin digestion of bromoacetanilide-inactivated NAT1 and sequencing by ESI MS/MS identified Cys-68 as the primary site of adduct formation. Additional proteolysis of the bromoacetanilide-treated NAT1 led to the identification of a second modified peptide which was adducted at Cys-44. The data reveal substantial differences in the interactions of small hydrophobic alkylating reagents with hamster NAT1. |
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