engleski

Computational Insights into Substrate Specificity of Monoamine Oxidase B

Histamine is an important mediator of many biological processes including inflammation, gastric acid secretion, neuromodulation, and regulation of immune function. Due to its potent pharmacological activity even at very low concentrations, the degradation of histamine has to be carefully regulated to avoid adverse reactions. Two major routes of histamine inactivation in mammals are: (a) methylation of the imidazole ring, catalyzed by histamine N-methyltransferase (HMT), and (b) oxidative deamination of the primary amino group, catalyzed by diamine DAO oxidase (DAO). HMT catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to the secondary imidazole amino group forming N-methylhistamine, and is a highly specific enzyme that does not show significant methylation of other HMT substrates. N-methylhistamine is not active at the histamine receptor sites, and is further metabolized by monoamine oxidase (MAO), a primary degradation enzyme for a range of biogenic and dietary amines in cells, including amine neurotransmitters in the brain, which is why it has been the central pharmacological target for treating depression and Parkinson’s disease for over 60 years. The notion that histamine is essentially not a substrate for MAO, whereas N-methylhistamine is, raises the question of what is the origin of its unexpected MAO B selectivity towards two very similar compounds, yet completely identical in their reactive ethylamine chain parts.

MAO B ; histamine ; N-methylhistamine

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