Biosynthesis of a novel ganoderic acid by expressing CYP genes from Ganoderma lucidum in Saccharomyces cerevisiae.

Abstract

Ganoderic acids (GAs), a group of highly oxygenated lanostane-type triterpenoids from the traditional Chinese medicinal mushroom Ganoderma lucidum, possessed significant pharmacological activities. Due to the difficulty in its genetic manipulation, low yield, and slow growth of G. lucidum, biosynthesis of GAs in a heterologous host is a promising alternative for their efficient production. Heterologous production of a GA, 3-hydroxy-lanosta-8,24-dien-26-oic acid (HLDOA), was recently achieved by expressing CYP5150L8 from Ganoderma lucidum in Saccharomyces cerevisiae, but post-modification of HLDOA to biosynthesize other GAs remains unclear. In this study, another P450 from G. lucidum, CYP5139G1, was identified to be responsible for C-28 oxidation of HLDOA, resulting in the formation of a new GA 3,28-dihydroxy-lanosta-8,24-dien-26-oic acid (DHLDOA) by the engineered yeast, whose chemical structure was confirmed by UPLC-APCI-HRMS and NMR. In vitro enzymatic experiments confirmed the oxidation of HLDOA to DHLDOA by CYP5139G1. As the DHLDOA production was low (0.27mg/L), to improve it, the strategy of adjusting the dosage of hygromycin and geneticin G418 to respectively manipulate the copy number of plasmids pRS425-Hyg-CYP5150L8-iGLCPR (harboring CYP5150L8, iGLCPR, and hygromycin-resistant gene hygR) and pRS426-KanMx-CYP5139G1 (harboring CYP5139G1 and G418-resistant gene KanMx) was adopted. Finally, 2.2mg/L of DHLDOA was obtained, which was 8.2 fold of the control (without antibiotics addition). The work enriches the GA biosynthetic enzyme library, and is helpful to construct heterologous cell factories for other GA production as well as to elucidate the authentic GA biosynthetic pathway in G. lucidum. KEY POINTS: • Another P450 gene responsible for GA's post-modification was discovered and identified. • One new GA, DHLDOA, was identified and produced via engineered yeast. • With the balance of the two CYP genes expression, DHLDOA production was significantly improved.