Combinatorial Enzymatic Catalysis for Bioproduction of Ginsenoside Compound K

Immobilization of snailase and β-glucosidase on L-aspartic acid-modified magnetic amorphous ZIF for efficiently and sustainably producing ginsenoside compound K

Improving the catalytic efficiency and recyclability of immobilized enzyme remained a serious challenge in industrial applications. Enzyme immobilization in the amorphous zeolite imidazolate framework (aZIF) preserved high enzyme activity, but still faced separation difficulties and a low catalytic efficiency in practice. In this study, a one-pot co-precipitation method was used to form the enzyme-aZIF/magnetic nanoparticle (MNP) biocomposite by rapidly precipitating snailase (Sna) and β-glucosidase (β-G) with metal/ligand on MNP and modifying with L-aspartic acid (Asp). Thanks to Asp modification protecting the natural conformation of internal protein molecules and MNP stabilizing the conformation of active enzymes after immobilizing, Sna&β-G in the carrier had more stable conformations and higher catalytic efficiency than those in conventional ZIF-8, increasing the catalytic efficiency for converting ginsenoside Rb1 to rare ginsenoside compound K (CK) to 79.16 %. Moreover, while improving the stability of Sna&β-G, owing to the magnetism imparted by MNP, the immobilized enzyme maintained high enzyme activity and recovery after 7 cycles by rapid magnetic separation. The results provided guidance for developing immobilized Sna&β-G biocomposites with ideal catalytic efficiency and easy recovery to catalyze ginsenoside Rb1 to rare ginsenoside CK.

A GH1 β-glucosidase from the Fervidobacterium pennivorans DSM9078 showed extraordinary thermostability and distinctive ability in the efficient transformation of ginsenosides

A novel GH1 β-glucosidase Fpglu1 from Fervidobacterium pennivorans DSM9078 was successfully cloned and expressed in Escherichia coli. This hyperthermophilic enzyme possesses unique features that make it valuable in biochemistry and pharmacology. It exhibited optimal activity at temperatures exceeding 100 °C, a trait rarely observed in other enzymes, and demonstrated extraordinary thermostability. It displayed multifunctional activity, with the highest activity observed for p-nitrophenyl-β-d-glucopyranoside (pNPGlu) at 92.47 U/mg. Furthermore, the distinctive capacity of Fpglu1 to transform ginsenosides (Rb1, Rb2, and Rc) into Compound-K (C-K) sets it apart from the other enzymes. It effectively cleaved the external β-(1-6) glycosidic linkage at the C-20 position of ginsenosides Rb1, Rb2, and Rc, followed by hydrolysis ofthe internal glycosidic bond connected to the C-3 position. The kcat/Km value of Fpglu1 for Rb1 was 453 ± 1.27 mM-1/s, significantly higher than those of Fpglu1 for other ginsenosides. The crystal structure of Fpglu1, determined at 1.85 Å resolution, provided a deeper understanding of its catalysis and substrate specificity. The evaluation of the binding conformation, hydrogen bond, and key amino acids of β-glucosidase Fpglu1 with different ginsenosides (Rb1, Rb2, and Rc) further elucidated the structural basis of its substrate-binding preference. In summary, Fpglu1, which had excellent thermostability and unique ginsenoside-transforming ability, was a highly promising catalyst for the industrial production of ginsenoside C-K. Additionally, structural studies have laid a theoretical foundation for further improving the catalytic properties of the enzyme through directed evolution in the future.

Transcriptome Profiling, Cloning, and Characterization of AnGlu04478, a Ginsenoside Hydrolyzing β-Glucosidase from Aspergillus niger NG1306

β-Glucosidase plays a pivotal role in transforming ginsenosides into specific minor ginsenosides. In this study, total ginsenosides from Panax notoginseng leaves were used as substrates to stimulate the growth of Aspergillus niger NG1306. Transcriptome analysis identified a β-glucosidase gene, Anglu04478 (1455 bp, 484 amino acids, 54.5 kDa, pI = 5.1), as a participant in the ginsenosides biotransformation process. This gene was cloned and expressed in Escherichia coli BL21 Transetta (DE3). The AnGlu04478 protein was purified using a Ni2+ column, and its enzymatic properties were characterized. Purified AnGlu04478 exhibited a specific activity of 32.97 U/mg when assayed against pNPG. Under optimal conditions (pH 4.5, temperature 40 °C), the kinetic parameters, Km and Vmax, for pNPG were 1.55 mmol/L and 0.014 mmol/min, respectively. Cu2+ displayed an inhibitory effect on AnGlu04478, whereas Ca2+, Co2+, and Ni2+ ions had minimal impact. The enzyme showed tolerance to ethanol and was largely unaffected by glucose feedback inhibition. Testing with ginsenosides as substrates revealed selective hydrolysis at the C3 position of ginsenosides Rb1, Rb2, Rb3, and Rc, with the metabolic pathway delineated as Rb1 → GypXVII, Rb2 → C-O, Rb3 → C-Mx1 → C-Mx, and Rc → C-Mc1. The conversion rates of ginsenosides Rb1, Rb2, Rb3, and Rc varied from 2.58 to 20.63%. With 0.5 U purified enzyme and 0.5 mg total ginsenosides, incubated at 40 °C for 12 h, the conversion rates were 42.6% for GypXVII, 10.4% for C-O, 6.27% for C-Mx1, 26.96% for C-Mx, and 90% for Rc. These results suggest that AnGlu04478 displays substrate promiscuity as a β-glucosidase, thus broadening the potential for ginsenoside biotransformation.

A Versatile β-Glycosidase from Petroclostridium xylanilyticum Prefers the Conversion of Ginsenoside Rb3 over Rb1, Rb2, and Rc to Rd by Its Specific Cleavage Activity toward 1,6-Glycosidic Linkages

To convert ginsenosides Rb1, Rb2, Rb3, and Rc into Rd by a single enzyme, a putative β-glycosidase (Pxbgl) from the xylan-degrading bacterium Petroclostridium xylanilyticum was identified and used. The kcat/Km value of Pxbgl for Rb3 was 18.18 ± 0.07 mM-1/s, which was significantly higher than those of Pxbgl for other ginsenosides. Pxbgl converted almost all Rb3 to Rd with a productivity of 5884 μM/h, which was 346-fold higher than that of only β-xylosidase from Thermoascus aurantiacus. The productivity of Rd from the Panax ginseng root and Panax notoginseng leaf was 146 and 995 μM/h, respectively. Mutants N293 K and I447L from site-directed mutagenesis based on bioinformatics analysis showed an increase in specific activity of 29 and 7% toward Rb3, respectively. This is the first report of a β-glycosidase that can simultaneously remove four different glycosyls at the C-20 position of natural PPD-type ginsenosides and produce Rd as the sole product from P. notoginseng leaf extracts with the highest productivity.

Bioconversion, Pharmacokinetics, and Therapeutic Mechanisms of Ginsenoside Compound K and Its Analogues for Treating Metabolic Diseases

Rare ginsenoside compound K (CK) is an intestinal microbial metabolite with a low natural abundance that is primarily produced by physicochemical processing, side chain modification, or metabolic transformation in the gut. Moreover, CK exhibits potent biological activity compared to primary ginsenosides, which has raised concerns in the field of ginseng research and development, as well as ginsenoside-related dietary supplements and natural products. Ginsenosides Rb1, Rb2, and Rc are generally used as a substrate to generate CK via several bioconversion processes. Current research shows that CK has a wide range of pharmacological actions, including boosting osteogenesis, lipid and glucose metabolism, lipid oxidation, insulin resistance, and anti-inflammatory and anti-apoptosis properties. Further research on the bioavailability and toxicology of CK can advance its medicinal application. The purpose of this review is to lay the groundwork for future clinical studies and the development of CK as a therapy for metabolic disorders. Furthermore, the toxicology and pharmacology of CK are investigated as well in this review. The findings indicate that CK primarily modulates signaling pathways associated with AMPK, SIRT1, PPARs, WNTs, and NF-kB. It also demonstrates a positive therapeutic effect of CK on non-alcoholic fatty liver disease (NAFLD), obesity, hyperlipidemia, diabetes, and its complications, as well as osteoporosis. Additionally, the analogues of CK showed more bioavailability, less toxicity, and more efficacy against disease states. Enhancing bioavailability and regulating hazardous variables are crucial for its use in clinical trials.

Residue Effect-Guided Design: Engineering of S. Solfataricus β-Glycosidase to Enhance Its Thermostability and Bioproduction of Ginsenoside Compound K

β-Glycosidase from Sulfolobus solfataricus (SS-BGL) is a highly effective biocatalyst for the synthesis of compound K (CK) from glycosylated protopanaxadiol ginsenosides. In order to improve the thermal stability of SS-BGL, molecular dynamics simulations were used to determine the residue-level binding energetics of ginsenoside Rd in the SS-BGL-Rd docked complex and to identify the top ten critical contributors. Target sites for mutations were determined using dynamic cross-correlation mapping of residues via the Ohm server to identify networks of distal residues that interact with the key binding residues. Target mutations were determined rationally based on site characteristics. Single mutants and then recombination of top hits led to the two most promising variants SS-BGL-Q96E/N97D/N302D and SS-BGL-Q96E/N97D/N128D/N302D with 2.5-fold and 3.3-fold increased half-lives at 95 °C, respectively. The enzyme activities relative to those of wild-type for ginsenoside conversion were 161 and 116%, respectively..