Department of Biological Sciences, Brock University, St. Catharines, ON, L2S 3A1, Canada.
Department of Chemistry, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada.
New Phytol. 2023 Oct;240(2):757-769. doi: 10.1111/nph.19162. Epub 2023 Jul 30.
Mitragynine, an analgesic alkaloid from the plant Mitragyna speciosa (kratom), offers a safer alternative to clinical opioids such as morphine, owing to its more favorable side effect profile. Although kratom has been traditionally used for stimulation and pain management in Southeast Asia, the mitragynine biosynthesis pathway has remained elusive. We embarked on a search for mitragynine biosynthetic genes from the transcriptomes of kratom and other members of the Rubiaceae family. We studied their functions in vitro and in vivo. Our investigations led to the identification of several reductases and an enol methyltransferase that forms a new clade within the SABATH methyltransferase family. Furthermore, we discovered a methyltransferase from Hamelia patens (firebush), which catalyzes the final step. With the tryptamine 4-hydroxylase from the psychedelic mushroom Psilocybe cubensis, we accomplished the four-step biosynthesis for mitragynine and its stereoisomer, speciogynine in both yeast and Escherichia coli when supplied with tryptamine and secologanin. Although we have yet to pinpoint the authentic hydroxylase and methyltransferase in kratom, our discovery completes the mitragynine biosynthesis. Through these breakthroughs, we achieved the microbial biosynthesis of kratom opioids for the first time. The remarkable enzyme promiscuity suggests the possibility of generating derivatives and analogs of kratom opioids in heterologous systems.
来自植物Mitragyna speciosa（Kratom）的镇痛生物碱米那基林，由于其更有利的副作用谱，为临床阿片类药物（如吗啡）提供了更安全的替代选择。虽然Kratom 在东南亚一直被传统用于刺激和疼痛管理，但米那基林的生物合成途径仍然难以捉摸。我们从Kratom 和其他茜草科家族成员的转录组中寻找米那基林生物合成基因。我们在体外和体内研究了它们的功能。我们的研究导致鉴定了几个还原酶和烯醇甲基转移酶，它们在 SABATH 甲基转移酶家族内形成了一个新的分支。此外，我们发现了来自 Hamelia patens（火树）的甲基转移酶，它催化最后一步。当用色胺和 secologanin 供应时，我们与迷幻蘑菇 Psilocybe cubensis 的色胺 4-羟化酶一起，在酵母和大肠杆菌中完成了米那基林及其立体异构体 speciogynine 的四步生物合成。尽管我们尚未确定 Kratom 中的真实羟化酶和甲基转移酶，但我们的发现完成了米那基林的生物合成。通过这些突破，我们首次实现了 Kratom 阿片类药物的微生物生物合成。显著的酶混杂性表明在异源系统中生成 Kratom 阿片类药物的衍生物和类似物的可能性。
