Molecular basis of human MAO A and B.

Monoamine oxidase A and B (MAO A and B) catalyze the oxidative deamination of a number of biogenic and xenobiotic amines with different substrate and inhibitor specificities. Recently, cDNA clones that encode the human liver MAO A and B have been isolated. Comparison of the deduced amino acid sequences shows that they are 70% homologous and they appear to be derived from separate genes. Expression of functional enzymes by transient transfection of the cDNAs provide unequivocal evidence that the different catalytic activities of MAO A and B reside in their primary amino acid sequences. These two genes located on the X chromosome, Xp11.23, are deleted in some patients with Norrie disease. The possible role or the linkage of MAO genes to a number of diseases can now be investigated.