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There are two isoforms of monoamine oxidase (MAO, EC.18.104.22.168 ) in mammals, birds, amphibians and lizards, and only one form of MAO has been found in fish (Hall et al., 1982). Human MAO-A and MAO-B have 72% identity, and protein structures show great similarity (Binda et al., 2001, Ma et al., 2004) indicating the two forms arose from a gene duplication event.
Recently available predicted protein sequences from the coelacanth, Latimeria chalumnae, also indicate two MAO isoforms with 70-75% identity to human MAO-A, human MAO-B and zebrafish MAO. It is likely, therefore, that the duplication of the MAO gene occurred after the divergence of ray- and lobe-finned fish and before that of tetrapods and the coelacanth. Using timetree.org expert result (Hedges et al., 1982), we can estimate this occurred between 430.0 and 454.6 Mya.
Binda, C., Newton-Vinson, P., Hubálek, F., Edmondson, D. E., & Mattevi, A. (2001). Structure of human monoamine oxidase B, a drug target for the treatment of neurological disorders. Nature Structural & Molecular Biology, 9(1), 22-26.
Hall, T. R., Yurgens, P. B., Figueroa, H. R., Uruena, G., Olcese, J. M., Newton, D. K., & Vorwald, S. R. (1982). Monoamine oxidase types A and B in the vertebrate brain. Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 71(1), 107-110.
Hedges, S. B., Dudley, J., & Kumar, S. (2006). TimeTree: a public knowledge-base of divergence times among organisms. Bioinformatics, 22(23), 2971-2972.
Ma, J., Yoshimura, M., Yamashita, E., Nakagawa, A., Ito, A., & Tsukihara, T. (2004). Structure of rat monoamine oxidase A and its specific recognitions for substrates and inhibitors. Journal of molecular biology, 338(1), 103-114.
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This Observation was published on 8th November, 2013 at 15:52:25 and has been viewed 6518 times.
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Jones, T. (2013). Isoforms of monoamine oxidase (MAO) in coelacanth allow more precise dating of MAO gene duplication. PHILICA.COM Observation number 79.