Purification and characterization of an intracellular β-glucosidase from a new strain of Leuconostoc mesenteroides isolated from cassava

The lactic acid bacterium, Leuconostoc mesenteroides, when grown on an arbutin-containing medium, was found to produce an intracellular β-glucosidase. The enzyme was purified by chromatofocusing, ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular β-glucosidase, as estimated by gel filtration, was 360 kDa. The tetrameric structure of the β-glucosidase was determined following treatment of the purified enzyme with dodecyl sulphate (SDS). The intracellular β-glucosidase exhibited optimum catalytic activity at 50°C and pH 6 with citrate–phosphate buffer, and 5·5 with phosphate buffer. The enzyme was active against glycosides with (1→4)-β, (1→4)-α and (1→6)-α linkage configuration. From Lineweaver–Burk plots, K _m values of 0·07 mmol l⁻¹ and 3·7 mmol l⁻¹ were found for p -nitrophenyl-β- D -glucopyranoside and linamarin, respectively. The β-glucosidase was competitively inhibited by glucose and by D -gluconic acid–lactone and a glucosyl transferase activity was observed in the presence of ethanol. The β-glucosidase of Leuconostoc mesenteroides, with cyanogenic activity, could be of potential interest in cassava detoxification, by hydrolysing the cyanogenic glucosides present in cassava pulp.     

Purification and characterization of a feruloyl esterase from the fungus Penicilliumexpansum

An extracellular phenolic acid esterase produced by the fungus Penicillium expansum in solid state culture released ferulic and ρ-coumaric acid from methyl esters of theacids, and from the phenolic-carbohydrate esters O-[5-O-(trans-feruloyl)-α- l -arabinofuranosyl]-(1 → 3)-O-β- d -xylopyranosyl-(1 → 4)- d -xylopyranose (FAXX) and O-[5-O-((E)-ρ-coumaroyl)-α- l -arabinofuranosyl]-(1 → 3)-O-β- d -xylopyranosyl-(1 → 4)- d -xylopyranose(PAXX). The esterase was purified 360-fold in successive stepsinvolving ultrafiltration and column chromatography by gel filtration, anion exchange andhydrophobic interaction. These chromatographic methods separated the phenolic acid esterasefrom α- l -arabinofuranosidase, pectate and pectin lyase, polygalacturonase,xylanase and β- d -xylosidase activities. The phenolic acid esterase had an apparentmass of 65 kDa under non-denaturing conditions and a mass of 57·5 kDa underdenaturing conditions. Optimal pH and temperature were 5·6 and 37 °C,respectively and the metal ions Cu2+ and Fe³+ atconcentrations of 5 mmol l⁻¹ inhibited feruloyl esterase activity by 95% and44%, respectively, at the optimum pH and temperature. The apparent K_m and V_max of the purified feruloyl esterase for methyl ferulate at pH 5·6 and 37 °Cwere 2·6 mmol l⁻¹ and 27·1 μmol min⁻¹ mg⁻¹. The corresponding constants of ρ-coumaroylesterase for methyl coumarate were 2·9 mmol l⁻¹ and 18·6μmol min−1 mg⁻¹.     

Purification and characterization of an extracellular endo-1,4-β-xylanase from Fusarium oxysporum f. sp. melonis

Abstract Fusarium oxysporum f. sp. melonis produces extracellular endo-1,4-β-xylanase and β-xylosidase when grown in shaken culture at 26°C in a mineral salts medium containing oat spelt xylan and glucose as carbon sources. Endo-1,4-β-xylanase was purified 251 times from 5-day-old culture filtrates, by Sephacryl S-200, ion exchange and gel filtration HPLC. The purified sample yielded a single band in SDS polyacrylamide gels with a molecular mass of 80 kDa on electrophoretic mobility and 83 kDa by gel filtration behavior. High activity of the endo-1,4-β-xylanase against xylan was observed between 5 and 8 pH, and between 40 and 60°C, the optimum pH and temperature being 5.0 and 50°C, respectively. Kinetic properties of the enzyme are similar to those of other fungal xylanases, showing high affinity towards oat spelt xylan with a K _m of 1 mM expressed as xylose equivalent.     

Endo-(1 → 3)β-D-glucanase activity secreted by Bacillus sp. no. 215

The production of an extracellular endo-(1 → 3)-β-D-glucanase by Bacillus sp. no. 215 was induced during growth with (1 → 3)-β-D-glucan (curdlan) from Cellulomonas flavigena strain KU as carbon and energy source. Maximum levels of activity (0.26 U ml^-1 resp. 1.40 U mg^-1) were detected in cell-free culture supernatant fluid after 25 h of aerobic growth at 55°C. The cells secreted an endo-(1 → 3)-β-D-glucanase with low electrophoretic mobility that used curdlan from C. flavigena strain KU and from Agrobacterium sp. (formerly Alcaligenes faecalis var. myxogenes ) as substrates. The enzyme activity was highest at pH 7.0 and 55°C. It exhibited a remarkably low thermal stability with a half-life of 14 min at 55°C in the presence of substrate. Divalent metal cations were required for enzyme activity.     

Biochemical characterization of a β-fructofuranosidase from Rhodotorula dairenensis with transfructosylating activity

An extracellular β-fructofuranosidase from the yeast Rhodotorula dairenensis was characterized biochemically. The enzyme molecular mass was estimated to be 680 kDa by analytical gel filtration and 172 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, of which the N -linked carbohydrate accounts for 16% of the total mass. It displays optimum activity at pH 5 and 55–60 °C. The enzyme shows broad substrate specificity, hydrolyzing sucrose, 1-kestose, nystose, leucrose, raffinose and inulin. Although the main reaction catalyzed by this enzyme is sucrose hydrolysis, it also exhibits transfructosylating activity that, unlike other microbial β-fructofuranosidases, produces a varied type of prebiotic fructooligosaccharides containing β-(2→1)- and β-(2→6)-linked fructose oligomers. The maximum concentration of fructooligosaccharides was reached at 75% sucrose conversion and it was 87.9 g L⁻¹. The 17.0% (w/w) referred to the total amount of sugars in the reaction mixture. At this point, the amounts of 6-kestose, neokestose, 1-kestose and tetrasaccharides were 68.9, 10.6, 2.6 and 12.7 g L⁻¹, respectively.     

A New Steroidal Glycoside from Ophiopogon japonicus （Thunb.） Ker-Gawl.

To study the chemical constituents from traditional Chinese herb Ophiopogon japonicus （Thunb.） Ker-Gawl., a new steroidal glycoside, named ophiopojaponin C （1）, together with two known ones, was isolated by column chromatography. Spectroscopic and chemical evidence revealed the structures to be ophiopogenin 3-O-[α-L-rhamnopyranosyl（1→2）]-β-D-xylopyranosyl（1→4）-β-D-glucopyranoside （1）, diosgenin 3-O-[2-O-acetyl-α-L-rhamnopyranosyl（1→2）]-β-D-xylopyranosyl（1→3）-β-D-glucopyranoside （2）, and ruscogenin 1-O-[2-O-acetyl-α-L-rhamnopyranosyl（1→2）]-β-D-xylopyranosyl（1→3）-β-D-fucopyranoside （3）.     

Chemical Constituents of Schisandra rubriflora Rehd. et Wils.

Schisandra rubriflora Rehd. et Wils. is a traditional Chinese medicine. To search for new and bioactive components from traditional Chinese medicines and provide scientific evidence for taxonomy, the chemical constituents of the plant were investigated by various column chromatography methods (silica gel, Sephadex LH-20, and RP-18). From the aerial parts of S. rubriflora, three new megastigmane glycosides,namely (3S, 5R, 6S, 9R)-megastigmane-3, 9-diol 3-O-[α-L-arabionfuranosyl-(1→6)-β-D-glucopyranoside](1), 7-megastigmene-3-ol-9-one 3-O-[α-L-arabionfuranosyl-(1→6)-β-D-glucopyranoside] (2), and megastigmane-3α, 4β, 9ξ-tfiol 3-O-β-D-glucopyranoside (3), along with 14 known compounds, were isolated.The structures of the new compounds were elucidated by a combination of spectroscopic and chemical methods.     

An enzyme system hydrolysing the polysaccharides of Xanthomonas species

Enzymes hydrolysing the exopolysaccharides of Xanthomonas campestris and related species (xanthan) have been obtained from a Bacillus species isolated by enrichment culture. Growth on xanthan induced a number of enzymes acting on the xanthan molecule. These included one or more β-glucanohydrolases and β-glucosidases, together with mannosidases. The former activities were also present in cultures grown in the presence of laminaran or scleroglucan, but not in simple synthetic media with glucose as substrate. Partial purification of the enzymes active on glucans was achieved by ammonium sulphate precipitation and chromatography on DEAE-sepharose and CM-sepharose. The specificity of the β-glucosidase and the β-glucanohydrolase were investigated. Several β-glucans were hydrolysed to glucose and disaccharides, but there was no activity against β→ 6 linked polymers, cellulose azure or microcrystalline cellulose. Carboxymethylcellulose was hydrolysed, as were laminaran, scleroglucan and pachyman. Activity was greater against the β→ 4 linked glucans than against the β→ 3 linked glucans tested. As periodate-oxidized laminarin was also hydrolysed, it was concluded that the glucanohydrolase acted as an endo enzyme. The β-glucosidase had a pH optimum at about 8–2 and a temperature optimum at 45°C; it showed higher activity against o -nitrophenyl-D-glucopyranoside, cellobiose, trehalose and sophorose than against gentibiose.     

Intracellular X-prolyl dipeptidyl peptidase from Lactococcus lactis spp. lactis: purification and properties

An X-prolyl dipeptidyl peptidase (EC 3.4.14.5) has been purified from a crude intracellular extract from Lactococcus lactis spp. lactis NCDO 763 by ion-exchange chromatography and gel filtration. One protein band was detected after electrophoresis of the purified enzyme in the presence or absence of sodium dodecyl sulphate. The enzyme is a 190 kDa dimer composed of identical subunits. Optimal activity occurs at pH 8.5 and 40–45°C and the enzyme is inhibited by reagents specific for serine proteases, such as diisopropylfluorophosphate. The enzyme hydrolyzes p -nitroanilide- or β-naphthylamide-substituted X-Pro dipeptides, as well as β-casomorphin.     

Glycolipids Isolated from Aplysia kurodaiCan Activate Cyclic Adenosine 3', 5'-Monophosphate-Dependent Protein Kinase from Rat Brain

Abstract: Cyclic AMP (cAMP)-dependent protein kinase (cAMP-kinase) partially purified from the membrane fractions of rat brains was stimulated by novel phosphonogly-cosphingolipids (glycolipids) derived from the skin and nerve fibers of Aplysia kurodai. Among various glycolipids tested, a major glycolipid from the skin, 3-O-MeGalβ 1→3GalNAcα 1→3 [6'- O -(2-aminoethylphosphonyl) Galα1→2] (2-aminoethylphosphonyl→6) Glcβ 1→4GICβ1→1ceramide (SGL-II), was most potent, giving half-maximal activation at 32.2 μ M. Activation of cAMP-kinase was maximal with 250 μ M SGL-II using kemptide as substrate. The effect of SGL-II was additive on kinase activity at submaximal concentrations of cAMP. The kinase activity activated with SGL-II was inhibited by the addition of protein kinase inhibitor peptide, a specific peptide inhibitor for cAMP-kinase. Its inhibitory pattern was similar to that for the catalytic subunit. Of the various substrates tested, the glycolipid-stimulated cAMP-kinase could phosphorylate microtubule-associated protein 2, synapsin I, and myelin basic protein but not histone H1 and casein. The regulatory subunit strongly inhibited the activity of purified catalytic subunit of cAMP-kinase. This inhibition was reversed by addition of SGL-II, as observed for cAMP. SGL-II was capable of partially dissociating cAMP-kinase, which was observed by gel filtration column chromatography. However, the binding activity of cAMP to the holoenzyme was not inhibited with SGL-II. These results demonstrate that the glycolipids can directly activate cAMP-kinase in a manner similar, but not identical, to that of cAMP.     

Purification and characterization of β-amylase from leaves of potato (Solanum tuberosum)

Amylolytic activity is widely distributed in plants. In potato leaves ( Solanum tuberosum L.) the abundant amylolytic activity was found to be β-amylase (EC 3.2.1.2, a-1,4-D-glucan maltohydrolase). β-Amylase from potato leaves was purified to homogeneity for study of enzyme characteristics. The purification steps included ammonium sulphate precipitation, anion exchange chromatography, affinity chromatography and gel filtration. The end product of α-1,4-glucan degradation was maltose. The protein is a 111-kDa homo-dimer with a subunit molecular mass of 56 kDa and a pl of 5.6. The pH-optimum is 6.5 using p -nitrophenylmaltopentaoside (PNPG5) as substrate. The optimal temperature for hydrolysis is at 40°C. The enzyme is unstable at temperatures above 40°C. The K_nt-value for PNPG5 is 0.73 m M and the activity is inhibited by cyclodextrins. At a concentration of 1 m M , β-cyclodextrin is a stronger inhibitor than α-cyclodextrin (68 and 20% inhibition, respectively). Branched glucans (e.g. starch and amylopectin) are superior substrates as compared to long, essentially unbranched glucans (e.g. amylose). This study of the catalytic properties of β-amylase from potato leaves indicates the importance of β-amylase as a starch degrading enzyme.     

Determination of specificities of rabbit antisera against the O-antigenic polysaccharide from Escherichia coli O126

Abstract Rabbit polyclonal antibodies against the lipopolysaccharide of Escherichia coli O126 were serologically characterized by ELISA. The antibody specificities were determined by studying the inhibitory effects of the methyl glycosides of both anomeric configurations of the constituent monosaccharides and the oligosaccharides derived from the O-antigenic polysaccharides of E. coli O126. It was found that, amongst the monosaccharides, β- d -N-acetyl glucosamine was the most effective inhibitory sugar in the O126 polysaccharide and the major specificity of the polyclonal antibodies was found to be directed against the trisaccharide having the structure α- D -Gal p (1 → 3)-β- D -Glc pNAc(1→2)- D -Man p.     

Glycosides from Roots of Cyathula officinalis Kuan

Abstract: To search for new and bioactive compounds from traditional Chinese medicines, a new glycoside, 3-O-[α- L -rhamnopyranosyl-(1→3)-( n -butyl-β- D -glucopyranosiduronate)]-28-O-β- D -glucopyranosyloleanolic acid ( 1 ), was isolated from the roots of Cyathula officinalis Kuan, along with 3-O-(methyl-β- D -glucopyranosiduronate)-28-O-β- D -glucopyranosyl oleanolic acid ( 2 ), 3-O-β- D -glucopyranosyl oleanolic acid ( 3 ), 3-O-β- D -glucuronopyranosyl oleanolic acid ( 4 ), 3-O-[β- L -rhamnopyranosyl-(1→3)-(β- D -glucuronopyranosyl)] oleanolic acid ( 5 ), 3-O-(β- D -glucuronopyranosyl)-28-O-β- D -glucopyranosyl oleanolic acid ( 6 ), 28-O-β- D -glucuronopyranosyl-(1→4)-β- D -glucopyranosyl hederagenin ( 7 ), 3-O-[β- L -rhamnopyranosyl-(1→3)-β- D -glucuronopyranosyl]-28-O-β- D -glucopyranosyl oleanolic acid ( 8 ), and 3-O-[β- D -glucopyranosyl-(1→2)-α- L -rhamnopyranosyl-(1→3)-β- D -glucuronopyranosyl]-28-O-β- D -glucopyranosyl oleanolic acid ( 9 ). The structures of these compounds were determined based on spectral and chemical evidence. The 50 per cent growth-inhibiting (GI₅₀) of compounds 1 and 5 against MDA-MB-231 (a human breast cancer cell line) was 3.44 × 10^-4 and 4.66 × 10^-4 mol/L, respectively.
(Managing editor: Wei WANG)     

Purification and properties of a BT-glucosidase of Hanseniaspora vineae Van der Walt and Tscheuschner with the view to its utilization in fruit aroma liberation

The β-glucosidase of Hanseniaspora vineae was purified by ion-exchange chromatography and gel filtration. Its molecular weight was 295000 PT 15000, its optimum pH was between 6 and 6–5, and its optimum temperature was 55°C. The enzyme was active against different soluble glucosides with β(1–2), β(1–3), β(1–4), β(1–6) and even aP(1–4) configurations. A glucosyltransferase activity appeared in the presence of ethanol. The enzyme was constitutive but its synthesis was repressed by glucose.     

An exo-β-d-glucanase derived from Zea coleoptile walls with a capacity to elicit cell elongation

Cell wall proteins were extracted from maize coleoptiles, Zea mays L. B37 x MO 17, with high concentrations of LiCl. Ion-exchange, chromatofocusing and gel-filtration chromatography were employed extensively to purify exo-β-glucanase activity from the extract. The purified enzyme functioned as an exo-(1→3)-β-glucanase (E.C. 3.2.1.58) and as a glucosidase (E.C. 3.2.1.21) capable of extensive hydrolysis of the native Zea wall (1→3), (1→4)-β- d -glucan, yielding glucose as the final product. The exoglucanase also enhances elongation of maize coleoptile sections in both the presence and absence of exogenous IAA.     

A β-(1→4)-xylosyltransferase involved in the synthesis of arabinoxylans in developing barley endosperms

A β-(1→4)-xylosyltransferase (XylTase; EC 2.4.2.24) participating in the synthesis of arabinoxylans was investigated using microsomal membranes prepared from developing barley ( Hordeum vulgare L.) endosperms. The microsomal fraction transferred Xyl from uridine 5'-diphosphoxylose (UDP-Xyl) into exogenous β-(1→4)-xylooligosaccharides derivatized at their reducing ends with 2-aminopyridine. HPLC analysis showed chain elongation of pyridylaminated β-(1→4)-xylotriose (Xyl₃-PA) by repeated attachment of one to five single xylosyl residues depending on the reaction time, leading to the formation of Xyl₄₋₈-PA. Methylation analysis and enzymatic digestions with β-xylosidase (EC 3.2.1.37) and endo -β-(1→4)-xylanase (EC 3.2.1.8) confirmed that the transfer of xylosyl residues into the newly synthesized products occurred through β-(1→4)-linkages. The activity of the XylTase was maximal at pH 6.8 and 20°C and most enhanced in the presence of 0.5% Triton X-100 and 5 m M MnCl₂. The apparent Michaelis constant and maximal velocity of the enzyme for Xyl₃-PA were 2.1 m M and 25 400 pmol min⁻¹ mg protein⁻¹, respectively. The enzyme also transferred [¹⁴C]Xyl from UDP-[¹⁴C]Xyl into higher β-(1→4)-xylooligosaccharides and birchwood xylans through β-(1→4)-linkages. The enzyme activity varied according to the stage of development (7–35 days after flowering) of the endosperms. Maximal activity occurred at 13–16 days; no activity was detectable in mature seeds. A comparison of endosperms from 10 different cultivars of barley harvested 11–22 days after flowering showed no correlation between enzyme activity and the amount of Xyl in the cell walls.     

Two New Saponins from Lysimachia capillipes Hemsl.

To investigate the saponins from whole plants of Lysimachia capillipes Hemsl., two new saponins, named capilliposide E (1) and capilliposide F (2), were isolated. The structures of the new sa ponins were elucidated as 3 β, 22α-dihydroxy- 16α-acetat-28→ 13 -lactone-oleanane-3 -O- [β-D-glucopyranosyl(1→2)-α-L-arabinpyranoyl]-22-O-β-D-glucopyranoside (1) and 3 β, 22α-dihydroxy- 16α-acetat-28→ 13-1actone-oleanane-3-O- { [β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)]-α-L-arabinpyranoyl }-22-O-βD-glucopyranoside (2). The structures of these compounds were determined by 1D- and 2D-NMR, MS techniques, and chemical methods.     

Cloning, expression, and characterization of an aldehyde dehydrogenase from Escherichia coli K-12 that utilizes 3-Hydroxypropionaldehyde as a substrate

For efficient production of isoflavone aglycones from soybean isoflavones, we isolated three novel types of β-glucosidase (BGL1, BGL3, and BGL5) from the filamentous fungi Aspergillus oryzae. Three enzymes were independently displayed on the cell surface of a yeast Saccharomyces cerevisiae as a fusion protein with α-agglutinin. Three β-glucosidase-displaying yeast strains hydrolyzed isoflavone glycosides efficiently but exhibited different substrate specificities. Among these β-glucosidases, BGL1 exhibited the highest activity and also broad substrate specificity to isoflavone glycosides. Although glucose released from isoflavone glycosides are generally known to inhibit β-glucosidase, the residual ratio of isoflavone glycosides in the reaction mixture with BGL1-displaying yeast strain (Sc-BGL1) reached approximately 6.2%, and the glucose concentration in the reaction mixture was maintained at lower level. This result indicated that Sc-BGL1 assimilated the glucose before they inhibited the hydrolysis reaction, and efficient production of isoflavone aglycones was achieved by engineered yeast cells displaying β-glucosidase.