2-Naphthylamine, a compound found in cigarette smoke, decreases both monoamine oxidase A and B catalytic activity.
Cigarette smokers exhibit a lower monoamine oxidase (MAO; EC 1.4.3.4) activity than nonsmokers. MAO is located in the outer membrane of mitochondria and exists as two isoenzymes, MAO A and B. MAO A prefers 5-hydroxytryptamine (serotonin), and MAO B prefers phenylethylamine (PEA) as substrate. Dopamine is a substrate for both forms. 2-Naphthylamine is a carcinogen found in high concentrations in cigarette smoke. The results of this study show that 2-naphthylamine has the ability to inhibit mouse brain MAO A and B in vitro by mixed type inhibition (competitive and non-competitive). The Ki for MAO A was determined to be 52.0 microM and for MAO B 40.2 microM. The inhibitory effect of 2-naphthylamine on both MAO A and B catalytic activity, supports the hypothesis that smoking decreases MAO activity in vivo, instead that smokers with lower MAO activity are more prone to become a smoker.
Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, USA. hauptman@neotherapeutics.com
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D015081:2-Naphthylamine / Q000032:analysis / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000201:enzymology / Q000648:ultrastructure; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000201:enzymology; D008995:Monoamine Oxidase / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D010947:Plants, Toxic; D012906:Smoke / Q000032:analysis*; D014026:Nicotiana
D008996:Monoamine Oxidase Inhibitors; D012906:Smoke; D015081:2-Naphthylamine; D008995:Monoamine Oxidase