Bioconversion of ginsenoside Rc into Rd by a novel α-L-arabinofuranosidase, Abf22-3 from Leuconostoc sp. 22-3: cloning, expression, and enzyme characterization

Molecular cloning, expression, purification, and characterization of Bacillus subtilis hydrolyzed ginsenoside Rc of α-L-arabinofuranosidase in Escherichia coli

The α-L-arabinofuranosidase enzyme plays a crucial role in the degradation of ginsenosides. In this study, we successfully cloned and expressed a novel α-L-arabinofuranosidase bsafs gene (1503 bp, 501 amino acids, 55 kDa, and pI = 5.4) belonging to glycosyl hydrolase (GH) family 51 from Bacillus subtilis genome in Escherichia coli BL21 cells. The recombinant protein Bsafs was purified using Ni2+ sepharose fastflow affinity chromatography and exhibited a specific activity of 2.91 U/mg. Bsafs effectively hydrolyzed the α-L-arabinofuranoside at C20 site of ginsenoside Rc to produce Rd as the product. The Km values for hydrolysis of pNP-α-L-arabinofuranoside (pNPαAraf) and ginsenoside Rc were determined as 0.74 and 4.59 mmol/L, respectively; while the Vmax values for these substrates were found to be 24 and 164 μmol/min/mg, respectively; furthermore, the Kcat values for these enzymes were calculated as 22.3 and 1.58 S-1 correspondingly.

Novel Split Intein-Mediated Enzymatic Channeling Accelerates the Multimeric Bioconversion Pathway of Ginsenoside

Cascade reaction systems, such as protein fusion and synthetic protein scaffold systems, can both spatially control the metabolic flux and boost the productivity of multistep enzymatic reactions. Despite many efforts to generate fusion proteins, this task remains challenging due to the limited expression of complex enzymes. Therefore, we developed a novel fusion system that bypasses the limited expression of complex enzymes via a post-translational linkage. Here, we report a split intein-mediated cascade system wherein orthogonal split inteins serve as adapters for protein ligation. A genetically programmable, self-assembled, and traceless split intein was utilized to generate a biocatalytic cascade to produce the ginsenoside compound K (CK) with various pharmacological activities, including anticarcinogenic, anti-inflammatory, and antidiabetic effects. We used two types of split inteins, consensus atypical (Cat) and Rma DnaB, to form a covalent scaffold with the three enzymes involved in the CK conversion pathway. The multienzymatic complex with a size greater than 240 kDa was successfully assembled in a soluble form and exhibited specific activity toward ginsenoside conversion. Furthermore, our split intein cascade system significantly increased the CK conversion rate and reduced the production time by more than 2-fold. Our multienzymatic cascade system that uses split inteins can be utilized as a platform for regulating multimeric bioconversion pathways and boosting the production of various high-value substances.

Biotransformation, Pharmacokinetics, and Pharmacological Activities of Ginsenoside Rd Against Multiple Diseases

Panax ginseng C.A. Mey. has a history of more than 4000 years and is widely used in Asian countries. Modern pharmacological studies have proved that ginsenosides and their compounds have a variety of significant biological activities on specific diseases, including neurodegenerative diseases, certain types of cancer, gastrointestinal disease, and metabolic diseases, in which most of the interest has focused on ginsenoside Rd. The evidentiary basis showed that ginsenoside Rd ameliorates ischemic stroke, nerve injury, cancer, and other diseases involved in apoptosis, inflammation, oxidative stress, mitochondrial damage, and autophagy. In this review, we summarized available reports on the molecular biological mechanisms of ginsenoside Rd in neurological diseases, cancer, metabolic diseases, and other diseases. We also discussed the main biotransformation pathways of ginsenoside Rd obtained by fermentation.

Insights into Recent Studies on Biotransformation and Pharmacological Activities of Ginsenoside Rd

It is well known that ginsenosides—major bioactive constituents of Panax ginseng—are attracting more attention due to their beneficial pharmacological activities. Ginsenoside Rd, belonging to protopanaxadiol (PPD)-type ginsenosides, exhibits diverse and powerful pharmacological activities. In recent decades, nearly 300 studies on the pharmacological activities of Rd—as a potential treatment for a variety of diseases—have been published. However, no specific, comprehensive reviews have been documented to date. The present review not only summarizes the in vitro and in vivo studies on the health benefits of Rd, including anti-cancer, anti-diabetic, anti-inflammatory, neuroprotective, cardioprotective, ischemic stroke, immunoregulation, and other pharmacological effects, it also delves into the inclusion of potential molecular mechanisms, providing an overview of future prospects for the use of Rd in the treatment of chronic metabolic diseases and neurodegenerative disorders. Although biotransformation, pharmacokinetics, and clinical studies of Rd have also been reviewed, clinical trial data of Rd are limited; the only data available are for its treatment of acute ischemic stroke. Therefore, clinical evidence of Rd should be considered in future studies.

Two Key Amino Acids Variant of α-l-arabinofuranosidase from Bacillus subtilis Str. 168 with Altered Activity for Selective Conversion Ginsenoside Rc to Rd

α-l-arabinofuranosidase is a subfamily of glycosidases involved in the hydrolysis of l-arabinofuranosidic bonds, especially in those of the terminal non-reducing arabinofuranosyl residues of glycosides, from which efficient glycoside hydrolases can be screened for the transformation of ginsenosides. In this study, the ginsenoside Rc-hydrolyzing α-l-arabinofuranosidase gene, BsAbfA, was cloned from Bacilus subtilis, and its codons were optimized for efficient expression in E. coli BL21 (DE3). The recombinant protein BsAbfA fused with an N-terminal His-tag was overexpressed and purified, and then subjected to enzymatic characterization. Site-directed mutagenesis of BsAbfA was performed to verify the catalytic site, and the molecular mechanism of BsAbfA catalyzing ginsenoside Rc was analyzed by molecular docking, using the homology model of sequence alignment with other β-glycosidases. The results show that the purified BsAbfA had a specific activity of 32.6 U/mg. Under optimal conditions (pH 5, 40 °C), the kinetic parameters K_m of BsAbfA for pNP-α-Araf and ginsenoside Rc were 0.6 mM and 0.4 mM, while the K_cat/K_m were 181.5 s^-1 mM^-1 and 197.8 s^-1 mM^-1, respectively. More than 90% of ginsenoside Rc could be transformed by 12 U/mL purified BsAbfA at 40 °C and pH 5 in 24 h. The results of molecular docking and site-directed mutagenesis suggested that the E173 and E292 variants for BsAbfA are important in recognizing ginsenoside Rc effectively, and to make it enter the active pocket to hydrolyze the outer arabinofuranosyl moieties at C₂₀ position. These remarkable properties and the catalytic mechanism of BsAbfA provide a good alternative for the effective biotransformation of the major ginsenoside Rc into Rd.

Growth stimulation of Bifidobacterium from human colon using daikenchuto in an in vitro model of human intestinal microbiota

Daikenchuto (DKT) is a Japanese traditional herbal (Kampo) medicine containing ginseng, processed ginger, and Japanese or Chinese pepper. We aimed to determine how DKT affects human colonic microbiota. An in vitro microbiota model was established using fecal inocula collected from nine healthy volunteers, and each model was found to retain operational taxonomic units similar to the ones in the original human fecal samples. DKT was added to the in vitro microbiota model culture at a concentration of 0.5% by weight. Next-generation sequencing of bacterial 16S rRNA gene revealed a significant increase in the relative abundance of bacteria related to the Bifidobacterium genus in the model after incubation with DKT. In pure cultures, DKT significantly promoted the growth of Bifidobacterium adolescentis, but not that of Fusobacterium nucleatum or Escherichia coli. Additionally, in pure cultures, B. adolescentis transformed ginsenoside Rc to Rd, which was then probably utilized for its growth. Our study reveals the in vitro bifidogenic effect of DKT that likely contributes to its beneficial effects on the human colon.

Cloning and Characterization of a Ginsenoside-Hydrolyzing α-L-Arabinofuranosidase, CaAraf51, From Cellulosimicrobium aquatile Lyp51

Moutai Jiuqu is a famous aromatic raw material of Maotai flavor liquor in China. It is brewed at high temperature and contains many kinds of bacteria, molds, and yeasts. There are many useful glycoside hydrolases in these microfloras, from which efficient glycoside hydrolases can be screened for biotransformation of natural saponins. In this study, an α-L-arabinofuranosidase gene (CaAraf51, 1524 bp, 507 amino acid, 55.07 kDa, and pI = 4.8) was cloned from Cellulosimicrobium aquatile Lyp51, which was isolated from the Maotai Jiuqu. The CaAraf51 was heterogeneously expressed in E. coli BL21 (DE3) and purified by N-terminal His-tag with the Ni²⁺-affinity column chromatography. The results show that purified CaAraf51 has a 6.8-fold purification factor and specific activity of 15 U/mg. Under optimal conditions (pH 5.0, temperature 40 °C), kinetic parameters K_m of CaAraf51 for pNPαAraf and Rc were 1.1 and 0.57 mM, the V_max were 25 and 6.25 μmol/min/mg, respectively. 90% of 0.87 mg Rc substrate can be transformed by 9.6 U purified CaAraf51 in 1 mL reaction system under suitable conditions (30 °C, pH 7.5 phosphate buffer, 1 h). In addition, we also tested the effects of metal ions and chemical agents on the activity of CaAraf51. According to systematically studied its function and enzymatic properties, CaAraf51 has excellent value and potential of biotransformation Rc into Rd.

Highly efficient production of diverse rare ginsenosides using combinatorial biotechnology

The rare ginsenosides are recognized as the functionalized molecules after the oral administration of Panax ginseng and its products. The sources of rare ginsenosides are extremely limited because of low ginsenoside contents in wild plants, hindering their application in functional foods and drugs. We developed an effective combinatorial biotechnology approach including tissue culture, immobilization, and hydrolyzation methods. Rh2 and nine other rare ginsenosides were produced by methyl jasmonate-induced culture of adventitious roots in a 10 L bioreactor associated with enzymatic hydrolysis using six β-glycosidases and their combination with yields ranging from 5.54 to 32.66 mg L^-1 . The yield of Rh2 was furthermore increased by 7% by using immobilized BglPm and Bgp1 in optimized pH and temperature conditions, with the highest yield reaching 51.17 mg L^-1 (17.06% of protopanaxadiol-type ginsenosides mixture). Our combinatorial biotechnology method provides a highly efficient approach to acquiring diverse rare ginsenosides, replacing direct extraction from Panax plants, and can also be used to supplement yeast cell factories.

Enzymatic Biotransformation of Ginsenoside Rb2 into Rd by Recombinant α-L-Arabinopyranosidase from Blastococcus saxobsidens

In this study, we used a novel α-L-arabinopyranosidase (AbpBs) obtained from ginsenoside-converting Blastococcus saxobsidens that was cloned and expressed in Escherichia coli BL21 (DE3), and then applied it in the biotransformation of ginsenoside Rb₂ into Rd. The gene, termed AbpBs, consisting of 2,406 nucleotides (801 amino acid residues), and with a predicted translated protein molecular mass of 86.4 kDa, was cloned into a pGEX4T-1 vector. A BLAST search using the AbpBs amino acid sequence revealed significant homology with a family 2 glycoside hydrolase (GH2). The over-expressed recombinant AbpBs in Escherichia coli BL21 (DE3) catalyzed the hydrolysis of the arabinopyranose moiety attached to the C-20 position of ginsenoside Rb2 under optimal conditions (pH 7.0 and 40°;C). Kinetic parameters for α-Larabinopyranosidase showed apparent K_m and V_max values of 0.078 ± 0.0002 micrometer and 1.4 ± 0.1 μmol/min/mg of protein against p-nitrophenyl-α-L-arabinopyranoside. Using a purified AbpBs (1 μg/ml), 0.1% of ginsenoside Rb₂ was completely converted to ginsenoside Rd within 1 h. The recombinant AbpBs could be useful for high-yield, rapid, and low-cost preparation of ginsenoside Rd from Rb₂.

An L213A variant of β-glycosidase from Sulfolobus solfataricus with increased α-L-arabinofuranosidase activity converts ginsenoside Rc to compound K

Compound K (C-K) is a crucial pharmaceutical and cosmetic component because of disease prevention and skin anti-aging effects. For industrial application of this active compound, the protopanaxadiol (PPD)-type ginsenosides should be transformed to C-K. β-Glycosidase from Sulfolobus solfataricus has been reported as an efficient C-K-producing enzyme, using glycosylated PPD-type ginsenosides as substrates. β-Glycosidase from S. solfataricus can hydrolyze β-d-glucopyranoside in ginsenosides Rc, C-Mc₁, and C-Mc, but not α-l-arabinofuranoside in these ginsenosides. To determine candidate residues involved in α-l-arabinofuranosidase activity, compound Mc (C-Mc) was docking to β-glycosidase from S. solfataricus in homology model and sequence was aligned with β-glycosidase from Pyrococcus furiosus that has α-l-arabinofuranosidase activity. A L213A variant β-glycosidase with increased α-l-arabinofuranosidase activity was selected by substitution of other amino acids for candidate residues. The increased α-l-arabinofuranosidase activity of the L213A variant was confirmed through the determination of substrate specificity, change in binding energy, transformation pathway, and C-K production from ginsenosides Rc and C-Mc. The L213A variant β-glycosidase catalyzed the conversion of Rc to Rd by hydrolyzing α-l-arabinofuranoside linked to Rc, whereas the wild-type β-glycosidase did not. The variant enzyme converted ginsenosides Rc and C-Mc into C-K with molar conversions of 97%, which were 1.5- and 2-fold higher, respectively, than those of the wild-type enzyme. Therefore, protein engineering is a useful tool for enhancing the hydrolytic activity on specific glycoside linked to ginsenosides.

Classification of glycosidases that hydrolyze the specific positions and types of sugar moieties in ginsenosides

Ginsenosides are the main compounds with pharmacological activities in ginseng. Deglycosylated ginsenosides, which are more pharmacologically active than glycosylated ginsenosides, can be produced by the specific or nonspecific hydrolysis of the sugar moieties in glycosylated ginsenosides using glycosidases. The enzymes that hydrolyze specifically ginsenosides with different types can be classified according to the enzymatic activity on the positions, inner and outer residues and types of sugar moieties in ginsenosides. Glycosylated ginsenosides are also hydrolyzed to deglycosylated ginsenosides with different hydrolytic pathways by cell conversion or fermentation. The biochemical properties of glycosidases involved in ginsenoside hydrolysis - ginsenosidases - were newly arranged and reviewed in accordance with different types. The combination of different-type ginsenosidases is suggested herein as an efficient tool to produce industrially important ginsenosides.

Identification and characterization of a ginsenoside-transforming β-glucosidase from Pseudonocardia sp. Gsoil 1536 and its application for enhanced production of minor ginsenoside Rg2(S)

The ginsenoside Rg₂(S), which is one of the pharmaceutical components of ginseng, is known to have neuroprotective, anti-inflammation, and anti-diabetic effects. However, the usage of ginsenoside Rg₂(S) is restricted owing to the small amounts found in white and red ginseng. To enhance the production of ginsenoside Rg₂(S) as a 100 gram unit with high specificity, yield, and purity, an enzymatic bioconversion method was developed to adopt the recombinant glycoside hydrolase (BglPC28), which is a ginsenoside-transforming recombinant β-glucosidase from Pseudonocardia sp. strain Gsoil 1536. The gene, termed bglPC28, encoding β-glucosidase (BglPC28) belonging to the glycoside hydrolase family 3 was cloned. bglPC28 consists of 2,232 bp (743 amino acid residues) with a predicted molecular mass of 78,975 Da. This enzyme was overexpressed in Escherichia coli BL21(DE3) using a GST-fused pGEX 4T-1 vector system. The optimum conditions of the recombinant BglPC28 were pH 7.0 and 37°C. BglPC28 can effectively transform the ginsenoside Re to Rg₂(S); the K_m values of PNPG and Re were 6.36±1.10 and 1.42±0.13 mM, respectively, and the V_max values were 40.0±2.55 and 5.62±0.21 µmol min⁻¹ mg⁻¹ of protein, respectively. A scaled-up biotransformation reaction was performed in a 10 L jar fermenter at pH 7.0 and 30°C for 12 hours with a concentration of 20 mg/ml of ginsenoside Re from American ginseng roots. Finally, 113 g of Rg₂(S) was produced from 150 g of Re with 84.0±1.1% chromatographic purity. These results suggest that this enzymatic method could be usefully exploited in the preparation of ginsenoside Rg₂(S) in the cosmetics, functional food, and pharmaceutical industries.

Characterization of a ginsenoside-transforming β-glucosidase from Paenibacillus mucilaginosus and its application for enhanced production of minor ginsenoside F₂

A novel β-glucosidase (BglPm) was identified from Paenibacillus mucilaginosus KCTC 3870(T) which has ginsenoside converting activity. The gene, termed bglPm, consists of 1,260 bp and belongs to glycoside hydrolase family 1 (GH1). After being overexpressed and purified from Escherichia coli, the enzymatic properties of BglPm were investigated. The enzyme exhibited an optimal activity at 45°C and pH 7.5 and showed high bioconversion ability for major ginsenoside Rb1 and Rd into ginsenoside F2. Thus, it was used for mass production of relatively high pure F2 from relatively abundant protopanaxadiol type ginsenosides mixture (PPDGM) with combined usage of ginsenoside Rc-hydrolyzing enzyme. Scale-up of production using 250 g of the PPDGM resulted in 152 g of F2 with 80.1% chromatography purity and 95.7% recovery. These results suggest that this enzyme would be useful in the preparation of pharmacologically active ginsenoside F2 in the functional food and pharmaceutical industries.

Recent biotechnological progress in enzymatic synthesis of glycosides

Glycosylation is one of the most important post-modification processes of small molecules and enables the parent molecule to have increased solubility, stability, and bioactivity. Enzyme-based glycosylation has achieved significant progress due to advances in protein engineering, DNA recombinant techniques, exploitation of biosynthetic gene clusters of natural products, and computer-based modeling programs. Our report summarizes glycosylation data that have been published within the past five years to provide an overall review of current progress. We also present the future trends and perspectives for glycosylation.

Mass production of the ginsenoside Rg3(S) through the combinative use of two glycoside hydrolases

The ginsenoside Rg3(S), which is one of the exceptional components of Korean red ginseng extract, has been known to have anti-cancer, anti-metastatic, and anti-obesity effects. An enzymatic bioconversion method was developed to obtain the ginsenoside Rg3(S) with a high specificity, yield, and purity. Two glycoside hydrolases (BglBX10 and Abf22-3) were employed to produce Rg3(S) as a 100g unit. The conversion reaction transformed ginsenoside Rc to Rd using Abf22-3, followed by Rb1 and Rd to Rg3(S), using BglBX10. It was performed in a 10L jar fermenter at pH 6.0 and 37°C for 24h, with a high concentration of 50mg/ml of purified ginsenoside mixture obtained from ginseng roots. Finally, 144g of Rg3(S) was produced from 250g of root extract with 78±1.2% chromatographic purity. These results suggest that this enzymatic method would be useful in the preparation of ginsenoside Rg3(S) for the functional food and pharmaceutical industries.