Human
arylamine N-acetyltransferase 1 (NAT1), present in all tissues, is classically described as a phase-II
xenobiotic metabolizing
enzyme but can also catalyze the hydrolysis of
acetyl-Coenzyme A (
acetyl-CoA) in the absence of an arylamine substrate using
folate as a cofactor. NAT1 activity varies inter-individually and has been shown to be overexpressed in
estrogen receptor-positive (ER+) breast
cancers. NAT1 has also been implicated in
breast cancer progression however the exact role of NAT1 remains unknown. The objective of this study was to evaluate the effect of varying levels of NAT1 N-acetylation activity in MDA-MB-231
breast cancer cells on global cellular metabolism and to probe for unknown endogenous NAT1 substrates. Global, untargeted metabolomics was conducted via ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) on MDA-MB-231
breast cancer cell lines constructed with
siRNA and CRISPR/Cas9 technologies to vary only in NAT1 N-acetylation activity. Many metabolites were differentially abundant in NAT1-modified cell lines compared to the Scrambled parental cell line.
N-acetylasparagine and
N-acetylputrescine abundances were strongly positively correlated (r = 0.986 and r = 0.944, respectively) with NAT1 N-acetylation activity whereas
saccharopine abundance was strongly inversely correlated (r = -0.876). Two of the most striking observations were a reduction in de novo
pyrimidine biosynthesis and defective β-oxidation of
fatty acids in the absence of NAT1. We have shown that NAT1 expression differentially affects cellular metabolism dependent on the level of expression. Our results support the hypothesis that NAT1 is not just a
xenobiotic metabolizing
enzyme and may have a role in endogenous cellular metabolism.