Isolation and characterization of novel ginsenoside-hydrolyzing glycosidase from Microbacterium esteraromaticum that transforms ginsenoside Rb2 to rare ginsenoside 20(S)-Rg3

Ginsenoside Rb2 was transformed by recombinant glycosidase (Bgp2) into ginsenosides Rd and 20(S)-Rg3. The bgp2 gene consists of 2,430 bp that encode 809 amino acids, and this gene has homology to the glycosyl hydrolase family 2 protein domain. SDS-PAGE was used to determine that the molecular mass of purified Bgp2 was 87 kDa. Using 0.1 mg ml^?1 of enzyme in 20 mM sodium phosphate buffer at 40 °C and pH 7.0, 1.0 mg ml^?1 ginsenoside Rb2 was transformed into 0.47 mg ml^?1 ginsenoside 20(S)-Rg3 within 120 min, with a corresponding molar conversion yield of 65 %. Bgp2 hydrolyzed the ginsenoside Rb2 along the following pathway: Rb2 → Rd → 20(S)-Rg3. This is the first report of the biotransformation of ginsenoside Rb2 to ginsenoside 20(S)-Rg3 using the recombinant glycosidase.     

Characterization of (2S,2'R,3'R)-2-(2',3'-[3H]-Dicarboxycyclopropyl)glycine Binding in Rat Brain

Abstract: [(2S,2′R,3′R)-2-(2′,3′-[³H]Dicarboxycyclopropyl)glycine ([³H]DCG IV) binding was characterized in vitro in rat brain cortex homogenates and rat brain sections. In cortex homogenates, the binding was saturable and the saturation isotherm indicated the presence of a single binding site with a K_D value of 180 ± 33 nM and a B_max of 780 ± 70 fmol/mg of protein. The nonspecific binding, measured using 100 µM LY354740, was <30%. NMDA, AMPA, kainate, l (?)-threo-3-hydroxyaspartic acid, and (S)-3,5-dihydroxyphenylglycine were all inactive in [³H]DCG IV binding up to 1 mM. However, several compounds inhibited [³H]DCG IV binding in a concentration-dependent manner with the following rank order of potency: LY341495 = LY354740 > DCG IV = (2S,1′S,2′S)-2-(2-carboxycyclopropyl)glycine > (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid > (2S,1′S,2′S)-2-methyl-2-(2-carboxycyclopropyl)glycine > l -glutamate = ibotenate > quisqualate > (RS)-α-methyl-4-phosphonophenylglycine = l (+)-2-amino-3-phosphonopropionic acid > (S)-α-methyl-4-carboxyphenylglycine > (2S)-α-ethylglutamic acid > l (+)-2-amino-4-phosphonobutyric acid. N-Acetyl-l -aspartyl-l -glutamic acid inhibited the binding in a biphasic manner with an IC₅₀ of 0.2 µM for the high-affinity component. The binding was also affected by GTPγS, reducing agents, and CdCl₂. In parasagittal sections of rat brain, a high density of specific binding was observed in the accessory olfactory bulb, cortical regions (layers 1, 3, and 4 > 2, 5, and 6), caudate putamen, molecular layers of the hippocampus and dentate gyrus, subiculum, presubiculum, retrosplenial cortex, anteroventral thalamic nuclei, and cerebellar granular layer, reflecting its preferential (perhaps not exclusive) affinity for pre- and postsynaptic metabotropic glutamate mGlu2 receptors. Thus, the pharmacology, tissue distribution, and sensitivity to GTPγS show that [³H]DCG IV binding is probably to group II metabotropic glutamate receptors in rat brain.     

Gas chromatographic-mass spectrometric determination of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol for study on human urinary excretion of ginsenosides after ingestion of ginseng preparations

An improved gas chromatographic-mass spectrometric method (GC-MS) with a fast solid-phase extraction on a newly introduced C₁₈ microcolumn, was applied to study the urinary excretion of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol glycosides in man after oral administration of ginseng preparations. Using panaxatriol as internal standard, 20(S)-protopanaxadiol and 20(S)-protopanaxatriol (the aglucones of ginesenosides) could be determined at a detection level of a few ng per ml urine by GC-MS with selected-ion monitoring after their release from glycosides which occur in urine. The extraction recovery of ginsenosides from urine was more than 80% and the intra-assay coefficient of variation was less than 5.0%. The results after intake of single doses of ginseng preparations demonstrated a linear relation between the amounts of ginsenosides consumed and the 20(S)-protopanaxatriol glycosides excreted in urine. About 1.2% of the dose was recovered in five days.     

Microbial transformation of ginsenoside Rb<Subscript>1</Subscript> by <Emphasis Type="Italic">Acremonium strictum</Emphasis>

Preparative-scale fermentation of ginsenoside Rb₁ (1) with Acremonium strictum AS 3.2058 gave three new compounds, 12β-hydroxydammar-3-one-20 (S)-O-β-d-glucopyranoside (7), 12β, 25-dihydroxydammar-(E)-20(22)-ene-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (8), and 12β, 20 (R), 25-trihydroxydammar-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (9), along with five known compounds, ginsenoside Rd (2), gypenoside XVII (3), ginsenoside Rg₃ (4), ginsenoside F₂ (5), and compound K (6). The structural elucidation of these metabolites was based primarily on one- and two-dimensional nuclear magnetic resonance and high-resolution electron spray ionization mass spectra analyses. Among these compounds, 2–6 are also the metabolites of ginsenoside Rb₁ in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, A. strictum might be a useful tool for generating mammalian metabolites of related analogs of ginsenosides for complete structural identification and for further use in pharmaceutical research in this series of compounds. In addition, the biotransformation kinetics was also investigated.     

Enzymatic biotransformation of ginsenoside Rb1 to 20(<Emphasis Type="Italic">S</Emphasis>)-Rg3 by recombinant β-glucosidase from <Emphasis Type="Italic">Microbacterium esteraromaticum</Emphasis>

Microbacterium esteraromaticum was isolated from ginseng field. The β-glucosidase gene (bgp1) from M. esteraromaticum was cloned and expressed in Escherichia coli BL21 (DE3). The bgp1 gene consists of 2,496 bp encoding 831 amino acids which have homology to the glycosyl hydrolase family 3 protein domain. The recombinant β-glucosidase enzyme (Bgp1) was purified and characterized. The molecular mass of purified Bgp1 was 87.5 kDa, as determined by SDS-PAGE. Using 0.1 mg ml⁻¹ enzyme in 20 mM sodium phosphate buffer at 37°C and pH 7.0, 1.0 mg ml⁻¹ ginsenoside Rb1 was transformed into 0.444 mg ml⁻¹ ginsenoside Rg3 within 6 h. The Bgp1 sequentially hydrolyzed the outer and inner glucose attached to the C-20 position of ginsenosides Rb1. Bgp1 hydrolyzed the ginsenoside Rb1 along the following pathway: Rb1 → Rd → 20(S)-Rg3. This is the first report of the biotransformation of ginsenoside Rb1 to ginsenoside 20(S)-Rg3 using the recombinant β-glucosidase.     

Preventive effect of 20(S)-ginsenoside Rg3 against lipopolysaccharide-induced hepatic and renal injury in rats

The preventive effect of 20(S)-ginsenoside Rg₃ (20(S)-Rg₃) on lipopolysaccharide (LPS)-induced oxidative tissue injury in rats was investigated in this study. The elevated serum nitrite/nitrate, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and creatinine levels in LPS-treated control rats were significantly decreased following 15 consecutive days of 20(S)-Rg₃ administration. In addition, thiobarbituric acid-reactive substance levels in the serum, liver and kidney were dose-dependently lower in 20(S)-Rg₃-treated groups than in the LPS-treated control group. The nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) protein expressions in the liver and kidney were significantly increased by LPS treatment. However, the 20(S)-Rg₃ administrations significantly decreased these protein expressions except for HO-1 in the liver. On the other hand, in the kidney, oral administration of 20(S)-Rg₃ showed a tendency to reduce NF-κB and iNOS protein expressions and also significantly reduced the elevated COX-2 and HO-1 protein expressions at a dose of 10 mg/kg body weight/day. All these results suggest the preventive effect of 20(S)-Rg₃ against LPS-induced acute oxidative damage in the liver and kidney and the preventive effect of 20(S)-Rg₃ administration against LPS toxicity was thought to be more predominant in the liver than kidney.     

The mechanism of acid-catalyzed conversion of ginsenoside Rf and two new 25-hydroxylated ginsenosides

Ginsenoside Rf is known to have higher chemical stability than other ginsenosides and until lately, the constituents in which it would convert were not known. Only in recent times, it was found that ginsenoside Rf converted to (20E)-Rg₉, (20Z)-Rg₉, Rg₁₀, and 20(R)-Rf. During my continued studies to update the chemical profile of red ginseng, two new ginsenosides converted from ginsenoside Rf, 25-hydroxylated ginsenosides, were discovered. These two new converted ginsenosides, namely (20E),25(OH)-ginsenoside Rg₉ (1), and (20Z),25(OH)-ginsenoside Rg₉ (2), together with ginsenosides (20E)-Rg₉ (3), (20Z)-Rg₉ (4), Rg₁₀ (5), and 20(R)-Rf (6) were isolated from a reaction mixture of ginsenoside Rf in an acid-catalyzed reaction. Their chemical structures (1 and 2) were elucidated by NMR and Mass spectral methods. Compounds 1 and 2 were presumably generated by hydration of (20E)-, and (20Z)-ginsenoside Rg₉. The presence of these six converted ginsenosides was confirmed by UPLC/TOF-MS method in red ginseng. On the basis of these results, I deduced the overall conversion mechanism of ginsenoside Rf and evaluated the significance of ginsenoside Rf as a characteristic mark substance of Panax ginseng.     

20(R)-Ginsenoside Rh2, not 20(S), is a selective osteoclastgenesis inhibitor without any cytotoxicity

Increased osteoclastic bone resorption plays a central role in the pathogenesis of many bone diseases, and osteoclast inhibitors are the most widely used treatments for these diseases. Ginsenosides, the main component of ginseng, have been known for their medicinal effects such as anti-inflammatory and anti-proliferative activities. In this study, we investigated the inhibitory effects of ginsenosides (ginsenoside 20(R)-Rh2 and ginsenoside 20(S)-Rh2) on osteoclastgenesis using RAW264 cells in vitro. Only ginsenoside 20(R)-Rh2 showed selective osteoclastgenesis inhibitory activity without any cytotoxicity up to 100 μM. These results implied that the stereochemistry of the hydroxyl group at C-20 may play an important role in selective osteoclastgenesis inhibitory activity.     

Effect of Amino Acids on Lysosomal Proteolytic Activities in Rat Livers

(R)-2-(4′-Isobutylphenyl)propanoic acid (ibuprofen), (S)-3(4′-isobutylphenyl)butanoic acid and (S)-4-(4′-isobutylphenyl)pentanoic acid were obtained using microbial oxidation of (±)-l-isobutyl-4-(1′ -methyloctyl)benzene by Rhodococcus sp. BPM 1613.     

Bacillus amyloliquefaciens SC06 alleviates the oxidative stress of IPEC-1 via modulating Nrf2/Keap1 signaling pathway and decreasing ROS production

Oxidative stress (OS) plays a major role in the gastrointestinal disorders. Although probiotics were reported to repress OS, few researches compared the antioxidant ability of different Bacillus strains and deciphered the mechanisms. To select a Bacillus strain with higher antioxidant capacity, we used H₂O₂ to induce intestinal porcine epithelial cell 1 (IPEC-1) OS model. The most suitable H₂O₂ concentration and incubation time were determined by the half lethal dose and methyl thiazolyl tetrazolium. Correlation analysis was performed to choose a sensitive indicator for OS. As for the comparison of Bacillus, cells were divided into control, Bacillus treatment, H₂O₂ treatment, and Bacillus pre-protection + H₂O₂ treatment. Bacillus were co-cultured with IPEC-1 for 3 h in Bacillus and Bacillus pre-protection + H₂O₂ treatments. Then, based on OS model, 300 μmol/L H₂O₂ was added into medium of H₂O₂ and Bacillus pre-protection + H₂O₂ treatments for another 12 h. Antioxidant and apoptosis gene expressions were detected to screen the target strain. Nuclear factor erythroid-derived 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein1 (Keap1) pathway, reactive oxygen species (ROS) production, mitochondrial membrane potential (Δψm), apoptosis, and necrosis were analyzed. Results revealed that heme oxygenase-1 (HO-1) gene expression had a positive correlation with H₂O₂ induction. Moreover, Bacillus amyloliquefaciens SC06 (SC06)-meditated IPEC-1 showed the best antioxidant capacity though modulating Nrf2 phosphorylation. Δψm was elevated, while ROS generation was reduced with SC06 pre-protection, resulting in decreased apoptosis and necrosis. Altogether, HO-1 expression could be regarded as an OS indicator. The regulation of Nrf2/Keap1 pathway and ROS production by SC06 are involved in alleviating OS of IPEC-1.

     

Andrographolide protects chondrocytes from oxidative stress injury by activation of the Keap1–Nrf2–Are signaling pathway

Recent studies have shown that andrographolide (AP) has the potential to be developed as a drug for therapy for osteoarthritis (OA). However, the role of AP in attenuating the progression of OA is still unknown. We hypothesized that its therapeutic effect may be associated with its antioxidant potential. In this study, we investigated the therapeutic effect of AP on chondrocytes injured by H₂O₂ and the association with the oxidation-related signaling pathways through the detection of cell proliferation, cell viability, the expression of oxidative stress-specific genes (Sod1, Cat, and malonaldehyde [Mda]) and proteins (superoxide dismutase [SOD], catalase [CAT]) after a culture period of 3 and 5 days, respectively. Further exploration of the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) messenger RNA and protein was also performed. The results showed that 0.625 µg/ml and 2.5 µg/ml of AP decreased oxidative stress injury of chondrocytes by increasing cell proliferation reduced by H₂O₂ and antioxidant enzyme activity, including SOD and CAT. Inflammation factors, such as matrix metallopeptidase 13 (Mmp13), tissue inhibitor of metalloproteinase 1 (Timp1), and interleukin-6 (Il6), were downregulated in the H₂O₂ group with AP, demonstrating a decrease in the progression of OA. Pathway analyses identified that the kelch-like ECH-associated protein 1 (Keap1)–Nrf2–antioxidant response element (Are) pathway is an important mediator in AP therapy on H₂O₂-induced OA. This study indicates that AP exerts protection effects on oxidative stress via activation of the Keap1–Nrf2–Are pathway in chondrocytes injured by H₂O₂, which may be promising for the therapy of OA.     

Modulation of Lipid Kinase PI4KIIα Activity and Lipid Raft Association of Presenilin 1 Underlies γ-Secretase Inhibition by Ginsenoside (20S)-Rg3

Amyloid β-peptide (Aβ) pathology is an invariant feature of Alzheimer disease, preceding any detectable clinical symptoms by more than a decade. To this end, we seek to identify agents that can reduce Aβ levels in the brain via novel mechanisms. We found that (20S)-Rg3, a triterpene natural compound known as ginsenoside, reduced Aβ levels in cultured primary neurons and in the brains of a mouse model of Alzheimer disease. The (20S)-Rg3 treatment induced a decrease in the association of presenilin 1 (PS1) fragments with lipid rafts where catalytic components of the γ-secretase complex are enriched. The Aβ-lowering activity of (20S)-Rg3 directly correlated with increased activity of phosphatidylinositol 4-kinase IIα (PI4KIIα), a lipid kinase that mediates the rate-limiting step in phosphatidylinositol 4,5-bisphosphate synthesis. PI4KIIα overexpression recapitulated the effects of (20S)-Rg3, whereas reduced expression of PI4KIIα abolished the Aβ-reducing activity of (20S)-Rg3 in neurons. Our results substantiate an important role for PI4KIIα and phosphoinositide modulation in γ-secretase activity and Aβ biogenesis.     

Highly selective microbial transformation of major ginsenoside Rb(1) to gypenoside LXXV by Esteya vermicola CNU120806

Aims

This study examined the biotransformation pathway of ginsenoside Rb₁ by the fungus Esteya vermicola CNU 120806.

Methods and Results

Ginsenosides Rb₁ and Rd were extracted from the root of Panax ginseng. Liquid fermentation and purified enzyme hydrolysis were employed to investigate the biotransformation of ginsenoside Rb₁. The metabolites were identified and confirmed using NMR analysis as gypenoside XVII and gypenoside LXXV. A mole yield of 95·4% gypenoside LXXV was obtained by enzymatic conversion (pH 5·0, temperature 50°C). Ginsenoside Rd was used to verify the transformation pathway under the same reaction condition. The product Compound K (mole yield 49·6%) proved a consecutive hydrolyses occurred at the C‐3 position of ginsenoside Rb₁.

Conclusions

Strain CNU 120806 showed a high degree of specific β‐glucosidase activity to convert ginsenosides Rb₁ and Rd to gypenoside LXXV and Compound K, respectively. The maximal activity of the purified glucosidase for ginsenosides transformation occurred at 50°C and pH 5·0. Compared with its activity against pNPG (100%), the β‐glucosidase exhibited quite lower level of activity against other aryl‐glycosides. Enzymatic hydrolysate, gypenoside LXXV and Compound K were produced by consecutive hydrolyses of the terminal and inner glucopyranosyl moieties at the C‐3 carbon of ginsenoside Rb₁ and Rd, giving the pathway: ginsenoside Rb₁→ gypenoside XVII → gypenoside LXXV; ginsenoside Rd→F₂→Compound K, but did not hydrolyse the 20‐C, β‐(1‐6)‐glucoside of ginsenoside Rb₁ and Rd.

Significance and Impact of the Study

The results showed an important practical application on the preparation of gypenoside LXXV. Additionally, this study for the first time provided a high efficient preparation method for gypenoside LXXV without further conversion, which also gives rise to a potential commercial enzyme application.     

Trends and methodological impacts in soil CO2 efflux partitioning: A metaanalytical review

Partitioning soil carbon dioxide (CO₂) efflux (R_S) into autotrophic (R_A; including plant roots and closely associated organisms) and heterotrophic (R_H) components has received considerable attention, as differential responses of these components to environmental change have profound implications for the soil and ecosystem C balance. The increasing number of partitioning studies allows a more detailed analysis of experimental constraints than was previously possible. We present results of an exhaustive literature search of partitioning studies and analyse global trends in flux partitioning between biomes and ecosystem types by means of a metaanalysis. Across all data, an overall decline in the R_H/R_S ratio for increasing annual R_S fluxes emerged. For forest ecosystems, boreal coniferous sites showed significantly higher (P<0.05) R_H/R_S ratios than temperate sites, while both temperate or tropical deciduous forests did not differ in ratios from any of the other forest types. While chronosequence studies report consistent declines in the R_H/R_S ratio with age, no difference could be detected for different age groups in the global data set. Different methodologies showed generally good agreement if the range of R_S under which they had been measured was considered, with the exception of studies estimating R_H by means of root mass regressions against R_S, which resulted in consistently lower R_H/R_S estimates out of all methods included. Additionally, the time step over which fluxes were partitioned did not affect R_H/R_S ratios consistently. To put results into context, we review the most common techniques and point out the likely sources of errors associated with them. In order to improve soil CO₂ efflux partitioning in future experiments, we include methodological recommendations, and also highlight the potential interactions between soil components that may be overlooked as a consequence of the partitioning process itself.     

Selective distortion of the planar group CαC'(O)O to a chiral flat tetrahedron in the amino acid alanine

Based on a Cambridge Structural Database (CSD) search, a meta‐analysis of 116 structures of alanine H₃NC_αH(CH₃)C′(O)O and its derivatives H₃NC_αH(CH₃)C′(O)O(H/R/M), protonated, esterified, or coordinated at the carboxylic group, shows that in the first step of a chirality chain, the L configuration at C_α induces (M) and (P) conformations with respect to rotation around the central C′─C_α bond. In the second step, the (M) and (P) conformations selectively distort the planar carboxylic group C_αC'(O_cis)O_trans to asymmetric flat (R) and (S) tetrahedra. High diastereoselectivities are caused by the two players attraction N…O_cis and repulsion O_trans…C_Me, which work together in (L,M,R) configurations but against each other in (L,P,S) configurations.     

20(R)-Ginsenoside Rg3 protects SH-SY5Y cells against apoptosis induced by oxygen and glucose deprivation/reperfusion

As shown in our previous studies, 20(R)-ginsenoside Rg3 [20(R)-Rg3] exerts a neuroprotective effect on a rat model of transient focal cerebral ischemia, and the mechanism through which it decreases the mRNA expression of calpain I and caspase-3 has been delineated. However, researchers do not know whether 20(R)-Rg3 exhibits a neuroprotective effect following oxygen-glucose deprivation and reperfusion (OGD/R) injury in vitro. In the present study, 20(R)-Rg3 increased cell viability, decreased the LDH leakage rate, and inhibited the apoptosis rate in a concentration-dependent manner. In addition, 20(R)-Rg3 markedly decreased cleaved caspase-3 protein expression. Furthermore, 20(R)-Rg3 significantly decreased the Bax mRNA and protein levels and increased the levels of Bcl-2 mRNA and protein, subsequently decreasing the Bax/Bcl-2 protein ratio. Based on these findings, 20(R)-Rg3 exerts a neuroprotective effect against OGD/R-induced apoptosis.     

Production of saponin in fermentation process of Sanchi (Panax notoginseng) and biotransformation of saponin byBacillus subtilis

An antitumor compound ginsenoside Rh₄ was produced during the fermentation process of Sanchi (Panax notoginseng) byBacillus subtilis. Saponins ginsenosides Rh₁ and Re were transformed byB. subtilis and were produced two main transformed products. the transformed product of ginsenoside Rh₁ was determined to be 3-O-β-D-glucopyranosyl-6-O-β-D-glucopyranosyl-20(S)-protopanaxatriol, and the transformed product of ginsenoside Re had 162 atomic mass units (amu) greater than the substrate. Compard with the substrates, the transformed products had one more glucosyl moiety linked respectively, which indicated that glycosylion reaction occurred in the transformation process.     

Quercetin alleviated H2O2‐induced apoptosis and steroidogenic impairment in goat luteinized granulosa cells

Quercetin (Que) is a natural flavonoid in most plants. Luteinized granulosa cell (LGC) culture is necessary for the study of follicle growth/differentiation. In the present study, we analyzed the role of Que in steroid production and apoptosis in hydrogen peroxide (H₂O₂)‐treated goat LGCs. The results showed that treatment with H₂O₂ induced apoptosis in goat LGCs, and treatment with Que decreased LGC apoptosis induced by H₂O₂ (P < .05), accompanied with the different expressions of BAX, BCL‐2, Caspase 3, and Cleaved caspase 3. Meanwhile, the messenger RNA expressions of nuclear factor erythroid 2 like 2 (Nrf2) and its downstream genes were upregulated with H₂O₂ +Que treatment, accompanied by the increased cellular viability (P < .05). Furthermore, Que alleviated H₂O₂‐induced reduction in the secretion of progesterone (P₄) (P < .05); however, it had no effect on the secretion of estrogen (E₂). Simultaneously, the expressions of StAR and P450scc were increased when treated with Que +H₂O₂, compared with the group treated with only H₂O₂ (P < .05). In conclusion, it is observed that Que could alleviate the H₂O₂‐induced apoptosis and steroidogenic impairment in goat LGCs, which might be mediated by the Nrf2 pathway.     

Characterization of a novel ginsenoside-hydrolyzing α-l-arabinofuranosidase, AbfA, from Rhodanobacter ginsenosidimutans Gsoil 3054T

The gene encoding an α-l-arabinofuranosidase that could biotransform ginsenoside Rc {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-[α-l-arabinofuranosyl-(1–6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol} to ginsenoside Rd {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol} was cloned from a soil bacterium, Rhodanobacter ginsenosidimutans strain Gsoil 3054^T, and the recombinant enzyme was characterized. The enzyme (AbfA) hydrolyzed the arabinofuranosyl moiety from ginsenoside Rc and was classified as a family 51 glycoside hydrolase based on amino acid sequence analysis. Recombinant AbfA expressed in Escherichia coli hydrolyzed non-reducing arabinofuranoside moieties with apparent K _m values of 0.53 ± 0.07 and 0.30 ± 0.07 mM and V _max values of 27.1 ± 1.7 and 49.6 ± 4.1 μmol min⁻¹ mg⁻¹ of protein for p-nitrophenyl-α-l-arabinofuranoside and ginsenoside Rc, respectively. The enzyme exhibited preferential substrate specificity of the exo-type mode of action towards polyarabinosides or oligoarabinosides. AbfA demonstrated substrate-specific activity for the bioconversion of ginsenosides, as it hydrolyzed only arabinofuranoside moieties from ginsenoside Rc and its derivatives, and not other sugar groups. These results are the first report of a glycoside hydrolase family 51 α-l-arabinofuranosidase that can transform ginsenoside Rc to Rd.     

Asymmetric epoxidation of cinnamyl alcohol with optically active titanium complexes

A family of titanium(IV) alkoxo compounds [{Ti(O‐i‐Pr)₂(OR)₂}₂] 1–4 prepared by alcohol exchange of Ti(O‐i‐Pr)₄ and a chiral higher‐boiling alcohol [ROH = 1,2:3,4‐di‐O‐isopropylidene‐α‐d ‐galactopyranose, 1,2:5,6‐di‐O‐isopropylidene‐α‐d ‐glucofuranose, (1R,2S,5R)‐(?)‐menthol, (1S‐endo)‐(?)‐borneol, (1S,2R,5S)‐(+)‐menthol, and (+)‐borneol] has been tested to evaluate their catalytic activity and stereoselectivity in the asymmetric epoxidation of cinnamyl alcohol. © 2005 Wiley‐Liss, Inc. Chirality