ABSTRACT
Immunochemical evidence that mitochondrial monoamine oxidase (MAO) A and B are different proteins has been accruing since the first report of R. McGauley and E. Racker in 1973. The surprisingly rapid oxidation of N-methyl-4-phenyltetrahydropyridine by MAO B prompted research in many laboratories aimed at redefining the specificity of the enzyme toward tertiary amines. Since the discovery of MAO 60 years ago, an extraordinary number of papers dealing with this enzyme have appeared, ranging from its biochemical aspects to immunochemical, histological, pharmacological, and clinical studies. The tendency of MAO B to polymerize has prevented the application of standard biophysical techniques to the determination of its native molecular weight. The origin of the notion that phospholipids are essential for the activity of MAO and that MAO A and B are the same protein with different lipids attached may be traced to certain experiments by Oreland and by Houslay and Tipton in the period 1971 to 1973.
