N,N-Dimethyltryptamine Production in Phalaris aquatica Seedlings
PLANT PHYSIOLOGY – October 01, 1988
Source: OpenAlex
Summary
In seedlings of *Phalaris aquatica*, enzyme activities peaked dramatically by day 5, with tryptophan decarboxylase converting substrates at 95 micromoles per hour, while N-methyl-transferases reached 1,000 and 2,200 micromoles. Intermediates also surged, with tryptamine and N-methyltryptamine hitting 25 and 53 micromolar, respectively. By day 8, DMT concentrations peaked at 650 micromolar before declining. The study highlights the crucial role of these enzymes in synthesizing DMT from tryptophan, which has implications for agriculture and plant-fungal interactions.
Abstract
The activities of three enzymes and the concentration of intermediates involved in the synthesis of N,N-dimethyltryptamine (DMT) from endogenous tryptophan (TRP) have been measured in vitro in seedlings of Phalaris aquatica L. cv Australian Commercial over 16 days after planting. The activities of tryptophan decarboxylase and the two N-methyl-transferases increased rapidly to maximal rates of substrate conversion at day 5 of 95, 1000, and 2200 micromoles per hour per milliliter, respectively. After these maximal rates, the activities decreased rapidly. The concentration of intermediates increased rapidly from zero in the seeds to maximal values of 25 and 53 micromolar at day 5 for tryptamine (T) and N-methyltryptamine (MT), respectively, 1000 micromolar at day 6 for TRP, and 650 micromolar at day 8 for DMT. The concentration of DMT and of all the intermediates in its synthesis declined rapidly after the maximal value had been reached. A mathematical model of the pathway from TRP to DMT using these enzymes correctly predicts the concentrations of T and MT, intermediates whose concentration is determined only by the pathway, and confirms that these three enzymes are responsible for the in vivo synthesis of DMT. Kinetic studies are reported for these enzymes. Tryptophan decarboxylase uses pyridoxal phosphate (PALP) as a coenzyme and has the following kinetic constants: K(m) (PALP) = 2.5 micromolar, K(m) (TRP) = 200 micromolar, K(i) (MT) = 5 millimolar, and K(i) (DMT) = 4 millimolar. The N-methyltransferases use S-adenosylmethionine (SAM) as substrate; S-adenosylhomocysteine (SAH) is assumed to be the product. The mechanism of secondary indolethylamine-N-methyltransferase, determined by initial velocity studies, is rapid equilibrium random with formation of both dead end complexes. Secondary indolethylamine-N-methyltransferase methylates both MT and 5-methoxy-N-methyltryptamine (5MeOMT). The kinetic constants for the methylation of MT are: K(MT) = 40 +/- 6, K(SAM) = 55 +/- 15, K(DMT) = 60, K(SAH) = 4.3 +/- 0.4 micromolar with unity interaction factors. The kinetic constants for the conversion of 5MeOMT to 5-methoxy-N,N-dimethyltryptamine (5MeODMT) are K(5MeOMT) = 40 +/- 10, K(SAM) = 90 +/- 40, and K(SAH) = 2.9 +/- 0.3 micromolar with unity interaction factors, except for SAM-5MeODMT = 2.0 +/- 0.9 and SAH-5MeOMT = 0.45 +/- 0.25. The kinetic constants for primary indolethylamine N-methyltransferase are K(m) (T) = 20, K(m) (SAM) = 40, K(i) (DMT) = 450 micromolar with the substrates binding independently.