AANAT kinetics of CoASH-targeted electrophiles of tryptamine and related analogs

• Published in: Bioorganic & medicinal chemistry letters Vol. 113; p. 129975
• Main Authors: Wandrey, Nicole, Hamilton, Luke, Boley, Jake, Haynes, Alexis, Redinger, Makenna, Hill, Mackinzi, Hagemeister, Mackenzie, Cole, Philip A., Moxley, Michael A., Thomas, Allen A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15-11-2024
• Subjects: Acetyl transferase; Circadian rhythm; Enzyme models; Melatonin; Melatonin; Circadian rhythm; Acetyl transferase; Enzyme models
• ISSN: 0960-894X; 1464-3405; 1464-3405
• DOI: 10.1016/j.bmcl.2024.129975

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•Bromoacetyltryptamine (BAT) was more potent than Michael acceptor analogs in an AANAT enzymatic assay.•A two-carbon linker connecting bromoacetyl and bicycle of BAT was shown to be optimal for enzymatic potency.•In comparison with BAT, Michael acceptor analogs were much slower to react with CoASH.•Kinetic simulation was used to develop a mechanism of AANAT’s alkyltransferase and acetyltransferase functions.
Arylalkylamine N-acetyltransferase (AANAT) catalyzes the rate-limiting step in melatonin synthesis and is a potential target for disorders involving melatonin overproduction, such as seasonal affective disorder. Previously described AANAT inhibitor bromoacetyltryptamine (BAT) and benzothiophenes analogs were reported to react with CoASH to form potent bisubstrate inhibitors through AANAT’s alkyltransferase function, which is secondary to its role as an acetyltransferase. We replaced the bromoacetyl group in BAT with various Michael acceptors to mitigate possible off-target activity of its bromoacetyl group. Additionally, we modified the length of the carbon linker between the Michael acceptor and indole bicycle of tryptamine to determine its effect on potency. An AANAT enzymatic assay showed a two-carbon linker present in BAT was optimal, while none of the new warheads had activity. Kinetic analysis indicated that these Michael acceptors reacted with CoASH much slower than BAT and not within the timeframe of our enzymatic assay. Additionally, we confirmed earlier reports that the acetyltransferase function of AANAT follows an ordered bi bi mechanism in which AcCoA binds before serotonin. In contrast, BAT’s alkyltransferase kinetics revealed a bi uni mechanism in which BAT binds to AANAT before CoASH. Our model combines both functions of AANAT into one kinetic mechanism.