NAT1, also known as N-acetyltransferase 1, is an enzyme that plays a crucial role in the biotransformation of many drugs, carcinogens, and other xenobiotics in the human body. NAT1 belongs to the family of N-acetyltransferases, which catalyze the transfer of an acetyl group from acetyl-CoA to an amine group of various compounds. NAT1 is found primarily in the liver, but it is also expressed in other tissues such as the gastrointestinal tract, lungs, kidneys, and brain. It plays a vital role in the detoxification and elimination of foreign compounds, including drugs and carcinogens, by catalyzing their acetylation and facilitating their excretion from the body. The activity of NAT1 can vary significantly among individuals due to genetic polymorphisms. These polymorphisms can affect the rate of drug metabolism and elimination, potentially leading to differences in drug efficacy and toxicity. Therefore, NAT1 genotyping has been used to predict drug response and toxicity in some clinical settings. In addition to its role in drug metabolism, NAT1 has also been implicated in the development of some cancers. Some studies have found associations between NAT1 polymorphisms and cancer risk, especially in combination with other genetic and environmental factors. However, the exact role of NAT1 in cancer development remains unclear and requires further investigation.