First Attempts at Isolating and Classifying MAO

Knowledge that deaminating chemicals exist in the tissue of various species has been known since the turn of the century. However it was first characterized in 1928 by M.C. Hare. She succeeded in extracting this enzyme from rabbit tissue and subsequently termed it tyramine oxidase.

In 1937 two other amine reducing oxidases were discovered, aliphatic amine oxidase and adrenaline oxidase but later in the same year they were discovered to be the same enzyme. In 1938 E. A. Zeller aptly termed the enyzme monoamine oxidase in order to distinguish it from the diamine oxidases as well as to better reflect is specificity.

More Recent Studies with MAO

Since the 1930s much research has been done regarding the inhibition of MAO especially in 1958 when its inhibition was discovered to alleviate the symptoms associated with clinical depression. Another ground-breaking study was conducted in 1968 when J.P. Johnston discovered that there existed two forms of the enzyme, MAO-A which is more sensitive to the the inhibitor clorgyline than the other form MAO-B which was later found to be more sensitive to deprenyl. Also the substrate selectivity of each subtype of this enzyme seems to be different as well. MAO-A reacts more with seratonin while MAO-B acts more on phenylethylene. In 1981 a genetic location was assigned to MAO-A on the X chromosome by J.E. Pintar and J. Barbarosa. Nevertheless the search continues for inhibitors of MAO that result in alleviation of the symptoms of clinical depression without the adverse side effects.

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