Lan N C, Chen C H, Shih J C
Division of Biological Sciences, School of Pharmacy, University of Southern California, Los Angeles 90033.
J Neurochem. 1989 May;52(5):1652-4. doi: 10.1111/j.1471-4159.1989.tb09223.x.
Monoamine oxidase (MAO) A and B are important enzymes that metabolize biogenic amines throughout the body. Previous studies had suggested that both MAO A and B consist of two subunits of molecular masses of 63 and 60 kilodaltons, respectively. The cDNAs encoding one subunit of human liver MAO A and B have been expressed in mammalian cells by transfection of the individual clones. The proteins expressed from these cDNAs are shown to be catalytically active. Similar to the endogenous enzymes, the expressed MAO A prefers serotonin as a substrate and is sensitive to the inhibitor clorgyline. In contrast, the expressed MAO B prefers phenylethylamine as a substrate and is sensitive to the inhibitor deprenyl. These results suggest that a single polypeptide of MAO A (or B), existing as either a monomer or homodimer, is enzymatically active. The ability to obtain functional MAO A and B from their respective cDNA clones allows us to study further the structure and function relationships of these important enzymes.
单胺氧化酶（MAO）A和B是在全身代谢生物胺的重要酶。先前的研究表明，MAO A和B分别由分子量为63和60千道尔顿的两个亚基组成。通过单个克隆的转染，编码人肝MAO A和B一个亚基的cDNA已在哺乳动物细胞中表达。从这些cDNA表达的蛋白质显示具有催化活性。与内源性酶相似，表达的MAO A优先选择血清素作为底物，并且对抑制剂氯吉兰敏感。相反，表达的MAO B优先选择苯乙胺作为底物，并且对抑制剂司来吉兰敏感。这些结果表明，以单体或同型二聚体形式存在的MAO A（或B）的单个多肽具有酶活性。从它们各自的cDNA克隆中获得功能性MAO A和B的能力使我们能够进一步研究这些重要酶的结构与功能关系。
