Highly Efficient One-Pot Bi-Enzymatic Cascade to 5-MeO-Tryptamine

Biocatalytic routes to tryptamine analogues are attractive for sustainable synthesis because they rely on renewable catalysts and can operate under mild aqueous conditions. However, their application is often limited by the enzyme substrate scope and process limitations. We developed a one-pot tandem two-enzyme cascade for the synthesis of 5-MeO-tryptamine from inexpensive substituted indole under mild and aqueous conditions. Exploiting its ability to work in the synthetic direction, we engineered Escherichia coli tryptophanase A (EcTnaA) to catalyze the synthesis of 5-MeO-tryptophan starting from the corresponding indole and l-serine. Previously reported Ruminococcus gnavus l-tryptophan decarboxylase (RgnTDC) was also engineered and combined with EcTnaA to obtain the final product of the cascade with yields up to 95% in 23 h. The cascade could be operated with 5-MeO-indole as a solid suspension (beyond its solubility limit) in pure aqueous buffer, which improved decarboxylase performance, with a yield of 88% in just 4 h, and a space–time yield (STY) of 2.1 g L–1 h–1, corresponding to a 35-fold increase in STY compared to previously reported methods. Enhanced-sampling computational techniques indicated that the selected RgnTDC W349Y increases gating-loop flexibility and open-state occupancy, providing a mechanistic rationale for the improved binding and release of bulkier substrates. These results establish an efficient and scalable biocatalytic route to 5-MeO-tryptamine and show how rational mutagenesis and solid-substrate, organic solvent-free setup can be combined to enable greener, low-cost production of tryptamine analogues.