When was MAO discovered?

In 1928, a graduate student at Duke University named M.C. Hare (Mary Bernheim) discovered a new enzyme in the liver of a rabbit, which she called ‘tyramine oxidase.’ But later in 1938 this enzyme was renamed ‘monoamine oxidase‘ by E. A. Zeller, in order to differentiate it from similar enzymes.

But in 1968, scientists discovered that there were two forms of this enzyme, which became known as MAO A and MAO B. The two types were found pharmacologically by Drs. J.P. Johnston, Joseph Knoll and K. Malman.  Drs. Jean Shih and Moussa Youdin separated the multiple forms of MAO biochemically.  This is where we first encounter Dr. Jean Chen Shih, who was then a post-doctoral researcher at UCLA working with Dr. Samuel Eiduson.