AUTHOR=Zou Gen , Ren Juanbao , Wu Di , Zhang Henan , Gong Ming , Li Wen , Zhang Jingsong , Yang Yan 

TITLE=Characterization and Heterologous Expression of UDP-Glucose 4-Epimerase From a Hericium erinaceus Mutant with High Polysaccharide Production

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2021.796278

DOI=10.3389/fbioe.2021.796278

ISSN=2296-4185

ABSTRACT=<p><italic>Hericium erinaceus</italic> is an important medicinal fungus in traditional Chinese medicine because of its polysaccharides and other natural products. Compared terpenoids and polyketides, the analysis of synthetic pathway of polysaccharides is more difficult because of the many genes involved in central metabolism. In previous studies, <italic>A6180</italic>, encoding a putative UDP-glucose 4-epimerase (UGE) in an <italic>H. erinaceus</italic> mutant with high production of active polysaccharides, was significantly upregulated. Since there is no reliable genetic manipulation technology for <italic>H. erinaceus</italic>, we employed <italic>Escherichia coli</italic> and <italic>Saccharomyces cerevisiae</italic> to study the function and activity of A6180. The recombinant overexpression vector pET22b-A6180 was constructed for heterologous expression in <italic>E. coli</italic>. The enzymatic properties of the recombinant protein were investigated. It showed that the recombinant A6180 could strongly convert UDP-α-D-glucose into UDP-α-D-galactose under optimal conditions (pH 6.0, 30°C). In addition, when <italic>A6180</italic> was introduced into <italic>S. cerevisiae</italic> BY4742, xylose was detected in the polysaccharide composition of the yeast transformant. This suggested that the protein coded by <italic>A6180</italic> might be a multifunctional enzyme. The generated polysaccharides with a new composition of sugars showed enhanced macrophage activity <italic>in vitro</italic>. These results indicate that A6180 plays an important role in the structure and activity of polysaccharides. It is a promising strategy for producing polysaccharides with higher activity by introducing <italic>A6180</italic> into polysaccharide-producing mushrooms.</p>