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Monoamine oxidase A and B share roughly 70% of their structure and both have substrate binding sites that are predominantly hydrophobic. Two tyrosine residues (398, 435 within MAO-B , 407 and 444 within MAO-A ) in the binding pocket that are commonly involved in inhibitor activity have been hypothesized to be relevant to orienting substrates ...
Extremely high levels of catecholamine can also be caused by neuroendocrine tumors in the adrenal medulla, a treatable condition known as pheochromocytoma. High levels of catecholamines can also be caused by monoamine oxidase A (MAO-A) deficiency, known as Brunner syndrome.
A few endogenous MAEs have been identified, including the trace amines β-phenylethylamine (PEA), tyramine, and tryptamine. [1] [11] At a concentration of 16 μM (1.6 × 10 −5 M), β-phenylethylamine has been shown to act as a MAE for norepinephrine (2.6-fold increase), dopamine (1.3-fold increase), and serotonin (2.3-fold increase) in the rat brainstem in vitro.
After release into the synaptic cleft, monoamine neurotransmitter action is ended by reuptake into the presynaptic terminal. There, they can be repackaged into synaptic vesicles or degraded by the enzyme monoamine oxidase (MAO), which is a target of monoamine oxidase inhibitors, a class of antidepressants. [citation needed]
In the case the catecholamines, however, the enzymes of degradation monoamine oxidase and catechol-O-methyl transferase, like the enzymes of synthesis, are intracellular. Not metabolism but uptake through cell membranes therefore is the primary means of their clearance from the extracellular space. The mechanisms were deciphered beginning in 1959.
Monoamine oxidase inhibitors (MAOIs) are a class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressants , especially for treatment-resistant depression and atypical depression . [ 1 ]
However, subsequent research indicated that the enzyme was involved in the oxidative deamination of additional monoamine neurotransmitters, including Catecholamines and histamine, as shown in the figure. The enzyme was eventually renamed as monoamine oxidase, indicating that the enzyme catalysed the oxidative deamination of the class of monoamines.
Monoamine oxidase A, also known as MAO-A, is an enzyme (E.C. 1.4.3.4) that in humans is encoded by the MAOA gene. [ 5 ] [ 6 ] This gene is one of two neighboring gene family members that encode mitochondrial enzymes which catalyze the oxidative deamination of amines , such as dopamine , norepinephrine , and serotonin .