Abstract
Hericium erinaceus 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, A6180, encoding a putative UDP-glucose 4-epimerase (UGE) in an H. erinaceus mutant with high production of active polysaccharides, was significantly upregulated. Since there is no reliable genetic manipulation technology for H. erinaceus, we employed Escherichia coli and Saccharomyces cerevisiae to study the function and activity of A6180. The recombinant overexpression vector pET22b-A6180 was constructed for heterologous expression in E. coli. 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 A6180 was introduced into S. cerevisiae BY4742, xylose was detected in the polysaccharide composition of the yeast transformant. This suggested that the protein coded by A6180 might be a multifunctional enzyme. The generated polysaccharides with a new composition of sugars showed enhanced macrophage activity in vitro. 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 A6180 into polysaccharide-producing mushrooms.
Highlights
Hericium erinaceus, which grows widely in the mountains of eastern Asia, is a valuable fungus for both medicinal and food use and has a long history in the field of medicine in China
The general culture conditions for the mycelium of H. erinaceus were 26°C and natural pH medium, and the results of the study showed that the optimum pH and optimum temperature of UDP-glucose 4-epimerase (UGE) were closer to the culture conditions
A predicted UDP-glucose-4-epimerases could be involved in the high yield of high-bioactivity polysaccharides in an H. erinaceus mutant
Summary
Hericium erinaceus, which grows widely in the mountains of eastern Asia, is a valuable fungus for both medicinal and food use and has a long history in the field of medicine in China. 2021), anti-fatigue properties (Liu et al, 2015), liver protection, and stomach protection (Chen et al, 2020). They have been widely used in medicine (Li et al, 2018; Jithendra et al, 2020), materials (Low et al, 2015), cosmetics, and other fields. The differentially expressed proteins A6180 involved in the mushroom polysaccharide biosynthetic pathways occurred in the mutant strain compared with the original strain, which belonged to GAL10 (UDP-glucose-4-epimerase) involved in the synthesis of polysaccharide repeat units, and upregulated mRNA and protein expression based on transcriptome and proteomics data (Gong et al, 2021). The function of this gene still needs to be verified through genetic engineering technology
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