In-vitro Characterizing of Thebaine Inhibition on Salutaridinol-7-O-acetyltransferase in Morphine Biosynthesis

Abstract

Opiates, such as morphine, have been used for medicinal purposes throughout human history. These bioactive compounds are produced in the opium poppy (Papaver somniferum) through complex biosynthetic pathways. This study aimed to characterize the in-vitro enzyme kinetics and inhibition of salutaridine reductase (SalR) and the coupled enzymes salutaridinol-7O-acetyltransferase (SalAT) and thebaine synthase (THS2). It was found that SalR exhibits substrate inhibition to salutaridine, while the coupled system of SalAT/THS2 demonstrated mixed model inhibition by the product thebaine. This inhibition was characterized using deuterated thebaine-d3. These findings could significantly enhance the potential for synthetic engineering of the alkaloid pathway and remove bottlenecks in production, offering a more adaptable approach to medicinal production via bacterial or yeast fermentation. This research provides valuable insights into the regulatory mechanisms of the morphine biosynthetic pathway and opens new avenues for the synthetic production of medicinal opiates.