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. Author manuscript; available in PMC: 2015 Oct 1.
Published in final edited form as: Pharmacogenomics J. 2014 Aug 26;15(2):189–195. doi: 10.1038/tpj.2014.44

Figure 4.

Figure 4

Potential mechanisms by which NAT1 modulates cotinine levels. (A) In subjects homozygous for the major NAT1 `A' allele, 75% of nicotine is broken down to cotinine and 25% to other metabolites. (B) The minor NAT1 `G' allele might affect cotinine levels by (1) regulating acetylation of an unknown nicotine metabolite or intermediate decreasing the breakdown of nicotine, resulting in a compensatory increase in cotinine formation; or (2) There might be an unknown intermediate that requires acetylation by NAT1 to further metabolize cotinine, and mutations in NAT1 could block this pathway, resulting in an accumulation of cotinine.