A fragment consisting of the first 204 amino-terminal amino acids of human arylamine N-acetyltransferase one (NAT1) and the first transacetylation step of catalysis

Abstract

Human arylamine N-acetyltransferase l (NAT1) has 290 amino acids and acetylates arylamines from acetyl coenzyme A. The acetyl group forms a thiolester with Cys 68 in the enzyme, and the acetyl group is then transferred to the arylamine. When NAT1 is expressed using the pGEX vector, the glutathione S-transferase (GST)-NATl fusion protein catalyses the acetylation of the NAT1 substrate p-aminobenzoic acid from acetyl CoA. Neither GST alone, nor a fusion protein of GST with the N-terminal 204 amino acids of NAT, catalyses the acetylation of p-aminobenzoic acid from acetyl CoA. Using [ 3H]acetyl CoA as substrate, it is shown that the full-length NAT1 and the N-terminal 204 amino acids of NAT1 each form an acetylated intermediate on reaction with acetyl CoA.