Cloning And Characterization Of A Phosphomevalonate Kinase Gene From Sanghuangporus Baumii

Sanghuangporus baumii, a macrofungus belonging to the Hymenochaetaceae family, has been widely used as a traditional medicine in Asia for centuries. Triterpenoids in S. baumii contribute to the pharmacological activities, however, their content is low in the fruiting body. Phosphomevalonate kinase (PMK) is an important rate-limiting enzyme in the triterpenoids synthesis pathway. In this study, a PMK gene (SbPMK) was cloned and analyzed. Sequence analysis showed that SbPMK has six exons and five introns. The 1,488 bp open reading frame encodes a 489 amino acid polypeptide with a predicted protein molecular weight of 52.47 kDa. The amino acid sequence of SbPMK shares highly similarity with that of PMK sequences from other species, especially in three functional motifs (MI, MII and MIII). The promoter of SbPMK contains typical cis-acting regulatory elements involved in MeJA responsiveness, light responsiveness, anaerobic induction, etc. Furthermore, recombinant SbPMK was overexpressed in Escherichia coli BL21, with a satisfactory solubility. During the fermentation culture of S. baumii, the biomass increased with fermentation and peaked on day 18 (4.80 g/L). The SbPMK expression and the triterpenoids content was peaked on day 6, and the triterpenoids content stabilized at 20.8 mg/g on day 18.