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Focus on the Melatonin Metabolite N 1-Acetyl-5-methoxykynuramine (AMK)

Rüdiger Hardeland*

DOI: 10.26717/BJSTR.2017.01.000318

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    • University of Goettingen, Goettingen, Germany
    • Corresponding author: Rüdiger Hardeland, Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Goettingen, Buergerstr 50, D-37073 Göttingen, Germany

Received: August 23, 2017;   Published: August 31, 2017

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The melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK) is a bioactive compound that acts as a potent inhibitor of cyclooxygenases, of neuronal NO synthase and myeloperoxidase, as a downregulator of cycloxygenase-2 and inducible NO synthase. Additionally, AMK is a potent scavenger of hydroxyl, peroxyl and carbonate radicals. It eliminates singlet oxygen more efficiently than histidine and related compounds. As a scavenger of all NO redox congeners, it forms a stable compound, 3-acetamidomethyl-6-methoxycinnolinone, that does not re-donate NO. Carbamoylating metabolites convert AMK into N-[2-(6-methoxyquinazolin-4-yl)-ethyl]-acetamide, another stable product. Upon oxidation, AMK forms an adduct-generating intermediate, which can attach to aromates, among them tyrosine and tryptophan. Protein AMKylation at tyrosines may cause inhibition of enzymes. With regard to receptor tyrosine kinases, this possibility may explain the observed growth inhibition in keratinocytes.

Keywords: AMK; Inflammation; NO synthases; Posttranslational modification; RNS; ROS

Abbreviations: AMK: N1 -acetyl-5-methoxykynuramine; CSF: Cerebrospinal Fluid; COX: Cyclooxygenase; iNOS : Inducible NO Synthase; MtiNOS: Mitochondrially Targeted Subform; nNOS: Neuronal NO synthase; ROS: Reactive Oxygen Species

|Abstract| |Introduction| |Inhibition and Downregulation of Enzymes| |Scavenging of Oxidizing Free Radicals| |Interactions with Reactive Nitrogen Species| |Stickiness of Oxidatively formed AMK Intermediates| |Conclusion| |References|