Pressor Amines by Amine Oxidase

In the presence of oxygen, decarboxylation of amino acids is followed by oxidative deamination to an aldehyde due to the action of amine oxidase. The existence of such an enzyme in animal tissues was first observed in 1928 by Hare-Bernheim (76), who used tyramine as substrate and therefore chose the name tyraminase. It was shown later (20) that a great variety of primary, secondary, and tertiary amines was subject to attack by this enzyme and consequently the name amine oxidase or monoamine oxidase. in contrast to diamine oxidase, was introduced. Only amines-with 

Monoamine oxidase is inhibited by octyl alcohol, but not by cyanide and, in contrast to diamine oxidase, also not by hydroxylamine. It is irreversibly denatured by urea (13). Optimal activity was found in alkaline solution near pH 8 (185). The enzyme was shown to be strongly activated by pyrrole (12) and this activation was sensitive to cyanide. 

The reaction mechanism has been formulated (149) as shown in the following equations  

Substituted amines reacted much slower than the free amines. The reaction velocity for a given amine depends on the partial oxygen pressure and is reduced to about one-third in air as compared to the speed in an oxygen atmosphere (108). Kohn (108) found the enzyme to be associated with insoluble material Alles and Heegaard (2) also noted activity only in turbid solutions.  

Amine oxidase was found in a variety of tissues (13,20,87,185) the highest concentrations occurred in liver and kidney. The kidneys of rats, however, in contrast to those from man (19), ox, pig, and sheep, seem to contain almost no, or only relatively little, amine oxidase (20,87,92,144, 185). 

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