Analysis of conserved active site residues in monoamine oxidase A and B and their three-dimensional molecular modeling.
Monoamine oxidase (MAO) is a key enzyme responsible for the degradation of serotonin, norepinephrine, dopamine, and phenylethylamine. It is an outer membrane mitochondrial enzyme existing in two isoforms, A and B. We have recently generated 14 site-directed mutants of human MAO A and B, and we found that four key amino acids, Lys-305, Trp-397, Tyr-407, and Tyr-444, in MAO A and their corresponding amino acids in MAO B, Lys-296, Trp-388, Tyr-398, and Tyr-435, play important roles in MAO catalytic activity. Based on the polyamine oxidase three-dimensional crystal structure, it is suggested that Lys-305, Trp-397, and Tyr-407 in MAO A and Lys-296, Trp-388, and Tyr-398 in MAO B may be involved in the non-covalent binding to FAD. Tyr-407 and Tyr-444 in MAO A (Tyr-398 and Tyr-435 in MAO B) may form an aromatic sandwich that stabilizes the substrate binding. Asp-132 in MAO A (Asp-123 in MAO B) located at the entrance of the U-shaped substrate-binding site has no effect on MAO A nor MAO B catalytic activity. The similar impact of analogous mutants in MAO A and MAO B suggests that these amino acids have the same function in both isoenzymes. Three-dimensional modeling of MAO A and B using polyamine oxidase as template suggests that the overall tertiary structure and the active sites of MAO A and B may be similar.
Geha
Rani Maurice
RM
Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles, California 90089-9121, USA.
Chen
Kevin
K
Wouters
Johan
J
Ooms
Frederic
F
Shih
Jean Chen
JC
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D002460:Cell Line; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000378:metabolism; D006801:Humans; D007313:Insecta; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008995:Monoamine Oxidase / Q000737:chemistry*; D009154:Mutation; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D000596:Amino Acids; D018076:DNA, Complementary; D020033:Protein Isoforms; D008995:Monoamine Oxidase