![]() |
|
|
K Chen, HF Wu, J Grimsby and JC Shih
Department of Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California, Los Angeles 90033.
A trout liver monoamine oxidase (MAO) cDNA was cloned by screening a cDNA library with a human MAO-A cDNA probe. The trout MAO cDNA encodes 499 amino acids, with a molecular mass of 56.6 kDa. The deduced amino acid sequence of trout MAO shows 70% and 71% identity with those of human MAO-A and MAO-B, respectively. Trout MAO contains the pentapeptide sequence Ser-Gly-Gly-Cys-Tyr, to which the cofactor FAD is covalently bound. Transient expression of the cDNA in COS-7 cells shows that trout MAO oxidizes both serotonin [5-hydroxytryptamine (5-HT)] and beta-phenylethylamine (PEA), unlike human MAO-A and MAO-B, which oxidize only 5-HT and PEA, respectively. The Km for 5-HT is similar for trout MAO (130 +/- 17 mM) and human MAO-A (68 +/- 4 mM). The Km for PEA is similar for trout MAO (12.5 +/- 2.0 mM) and human MAO-B (1.5 +/- 0.2 mM). When 5-HT is used as a substrate, trout MAO is more sensitive to clorgyline (IC50, 2.8 +/- 0.2 x 10(-8) M) than deprenyl (IC50, 1.0 +/- 0.1 x 10(-6) M), a result similar to the inhibition selectivity of human MAO-A. However, trout MAO is less sensitive to clorgyline than is human MAO-A (IC50, 5.8 +/- 0.1 x 10(-10) M). Trout MAO is less sensitive to deprenyl (IC50, 4.6 +/- 0.3 x 10(-7) M) than is human MAO- B (IC50, 1.4 +/- 0.1 x 10(-9) M) when PEA is used as the substrate. These results indicate that trout MAO displays substrate and inhibitor selectivities that are not identical to those of either MAO-A and -B, and it therefore represents a novel type of MAO. The structure of trout MAO will provide insights into the substrate and inhibitor selectivities of the MAOs.
This article has been cited by other articles:
![]() |
P.C. Hubbard, E.N. Barata, and A.V.M. Canario Olfactory Sensitivity to Catecholamines and their Metabolites in the Goldfish Chem Senses, March 1, 2003; 28(3): 207 - 218. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Tsugeno and A. Ito A Key Amino Acid Responsible for Substrate Selectivity of Monoamine Oxidase A and B J. Biol. Chem., May 30, 1997; 272(22): 14033 - 14036. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. Rebrin, R. M. Geha, K. Chen, and J. C. Shih Effects of Carboxyl-terminal Truncations on the Activity and Solubility of Human Monoamine Oxidase B J. Biol. Chem., July 27, 2001; 276(31): 29499 - 29506. [Abstract] [Full Text] [PDF] |
||||