Bioproduction platform using a novel cane toad (Rhinella marina) N-methyltransferase for psychedelic-inspired drug discovery

Abstract Psychedelic indolethylamines have emerged as potential medicines to treat several psychiatric pathologies. Natural sources of these compounds include ‘magic mushrooms’, plants used to prepare ahayuasca, and toads. Owing to the occurrence of indolethylamines such as N,N-dimethyltryptamine, toad skin and parotid gland preparations have a history of ceremonial use, yet their biosynthesis remains uncharacterized. We report the isolation of an indolethylamine N-methyltransferase (RmNMT) from cane toad (Rhinella marina). Unlike functionally similar mammalian and fungal enzymes, the efficiency and promiscuity of RmNMT made it suitable for the bioproduction of new-to-nature indolethylamine derivatives. N,N-Dimethylated indolethylamines showed reduced affinity and engagement at 5-HT1A and 5-HT2A receptors respectively, compared with primary amine equivalents. Despite reduced 5-HT2A receptor engagement of tertiary amines, only these molecules induced hallucinogenic behavior in mice underscoring the importance of metabolic stability. The discovery of RmNMT facilitated the establishment of a bioproduction platform for the isolation and pharmacological screening of novel indolethylamines.