title: 1,4-Benzoquinone as a new inhibitor of monoamine oxidase.
abstract: The effect of 1,4-benzoquinone (BQ) on type A and B monoamine oxidase (MAO-A and -B) in human brain synaptosomes was examined. MAO-A was found to be markedly inhibited by BQ competitively with the substrate, kynuramine, while MAO-B was less sensitive to this inhibitor and the inhibition was non-competitive with the substrate. The Ki value of MAO-A (9.62 +/- 0.35 microM) was much smaller than the Km value of the enzyme with the substrate (56.3 +/- 3.5 microM) or the Ki value of MAO-B with BQ (20.3 +/- 0.9 microM). The inhibition of MAO-A by BQ was also confirmed by the use of platelet mitochondria and clonal rat pheochromocytoma PC12h cells as enzyme sources. The inhibition of MAO activity by BQ proved to be reversible: the inhibited enzyme activity could be recovered by column chromatography on Sephadex G-25.
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000201:enzymology; D000818:Animals; D016227:Benzoquinones; D002999:Clone Cells / Q000201:enzymology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D007735:Kynuramine / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology; D008995:Monoamine Oxidase / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D010673:Pheochromocytoma / Q000201:enzymology; D010920:Placenta / Q000201:enzymology; D011809:Quinones / Q000494:pharmacology*; D051381:Rats
chemical_list: D016227:Benzoquinones; D007527:Isoenzymes; D008996:Monoamine Oxidase Inhibitors; D011809:Quinones; D007735:Kynuramine; C004532:quinone; D008995:Monoamine Oxidase