Enhancing the accumulation of β-amyrin in Saccharomyces cerevisiae by co-expression of Glycyrrhiza uralensis squalene synthase 1 and β-amyrin synthase genes

Glycyrrhiza uralensis Fisch. ex DC is widely used in traditional Chinese medicine (TCM). Among its various active components, glycyrrhizic acid is believed to be the marker component. Squalene synthase (SQS) and β-amyrin synthase (β-AS) are key enzymes in the biosynthetic pathway of glycyrrhizic acid in G. uralensis. To reveal the effects of co-expression of SQS1 and β-AS genes on this pathway, 7 yeast expression vectors harboring different SQS1 variants and β-AS were constructed and expressed in Saccharomyces cerevisiae as fusion proteins. TLC and GC-MS results showed that co-expression of SQS1 and β-AS enhanced the accumulation of β-amyrin. The effects of SQS12 were more obvious than the other two SQS1 variants. This study is significant for further investigations concerned with exploring the biosynthesis of glycyrrhizic acid in vitro and strengthening the efficacy of G. uralensis by means of increasing the content of glycyrrhizic acid.