title: Substrate and inhibitor specificities for human monoamine oxidase A and B are influenced by a single amino acid.
abstract: Monoamine oxidase (MAO) is responsible for the oxidation of biogenic and dietary amines. It exists as two isoforms, A and B, which have a 70% amino acid identity and different substrate and inhibitor specificities. This study reports the identification of residues responsible for conferring this specificity in human MAO A and B. Using site-directed mutagenesis we reciprocally interchanged three pairs of corresponding nonconserved amino acids within the central portion of human MAO. Mutant MAO A-I335Y became like MAO B, which exhibits a higher preference for beta-phenylethylamine than for the MAO A preferred substrate serotonin (5-hydroxytryptamine), and became more sensitive to deprenyl (MAO B-specific inhibitor) than to clorgyline (MAO A-specific inhibitor). The reciprocal mutant MAO B-Y326I exhibited an increased preference for 5-hydroxytryptamine, a decreased preference for beta-phenylethylamine, and, similar to MAO A, was more sensitive to clorgyline than to deprenyl. These mutants also showed a distinct shift in sensitivity for the MAO A- and B-selective inhibitors Ro 41-1049 and Ro 16-6491. Mutant pair MAO A-T245I and MAO B-I236T and mutant pair MAO A-D328G and MAO B-G319D reduced catalytic activity but did not alter specificity. Our results indicate that Ile-335 in MAO A and Tyr-326 in MAO B play a critical role in determining substrate and inhibitor specificities in human MAO A and B.
authors.affiliation: Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Geha
authors.forename: I
authors.initials: I
authors.lastname: Rebrin
authors.forename: K
authors.initials: K
authors.lastname: Chen
authors.forename: J C
authors.initials: JC
authors.lastname: Shih
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D016367:Baculoviridae / Q000235:genetics; D002384:Catalysis; D003010:Clorgyline / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005822:Genetic Vectors; D005998:Glycine / Q000737:chemistry; D006801:Humans; D007532:Isoleucine / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D008995:Monoamine Oxidase / Q000737:chemistry / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010627:Phenethylamines / Q000378:metabolism / Q000494:pharmacology; D020033:Protein Isoforms; D011619:Psychotropic Drugs / Q000494:pharmacology; D012642:Selegiline / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D012701:Serotonin / Q000378:metabolism; D013379:Substrate Specificity; D013912:Threonine / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D000596:Amino Acids; D008996:Monoamine Oxidase Inhibitors; D010627:Phenethylamines; D020033:Protein Isoforms; D011619:Psychotropic Drugs; D007532:Isoleucine; D012642:Selegiline; D013912:Threonine; D001224:Aspartic Acid; C029261:phenethylamine; D012701:Serotonin; D014443:Tyrosine; D008995:Monoamine Oxidase; D003010:Clorgyline; D005998:Glycine