Crystallisation of wild-type and variant forms of a recombinant plant enzyme β-D-glucan glucohydrolase from barley (Hordeum vulgare L.) and preliminary X-ray analysis

Wild-type and variant crystals of a recombinant enzyme beta-d-glucan glucohydrolase from barley (Hordeum vulgare L.) were obtained by macroseeding and cross-seeding with microcrystals obtained from native plant protein. Crystals grew to dimensions of up to 500 x 250 x 375 mum at 277 K in the hanging-drops by vapour-diffusion. Further, the conditions are described that yielded the wild-type crystals with dimensions of 80 x 40 x 60 mum by self-nucleation vapour-diffusion in sitting-drops at 281 K. The wild-type and recombinant crystals prepared by seeding techniques achived full size within 5-14 days, while the wild-type crystals grown by self-nucleation appeared after 30 days and reached their maximum size after another two months. Both the wild-type and recombinant variant crystals, the latter altered in the key catalytic and substrate-binding residues Glu220, Trp434 and Arg158/Glu161 belonged to the P4(3)2(1)2 tetragonal space group, i.e., the space group of the native microcrystals was retained in the newly grown recombinant crystals. The crystals diffracted beyond 1.57-1.95 A and the cell dimensions were between a = b = 99.2-100.8 A and c = 183.2-183.6 A. With one molecule in the asymmetric unit, the calculated Matthews coefficients were between 3.4-3.5 A(3).Da(-1) and the solvent contents varied between 63.4% and 64.5%. The macroseeding and cross-seeding techniques are advantageous, where a limited amount of variant proteins precludes screening of crystallisation conditions, or where variant proteins could not be crystallized.

Crystallization and preliminary X-ray analysis of Streptococcus mutans dextran glucosidase

Dextran glucosidase from Streptococcus mutans is an exo-hydrolase that acts on the nonreducing terminal alpha-1,6-glucosidic linkage of oligosaccharides and dextran with a high degree of transglucosylation. Based on amino-acid sequence similarity, this enzyme is classified into glycoside hydrolase family 13. Recombinant dextran glucosidase was purified and crystallized by the hanging-drop vapour-diffusion technique using polyethylene glycol 6000 as a precipitant. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 72.72, b = 86.47, c = 104.30 A. A native data set was collected to 2.2 A resolution from a single crystal.

Expression, purification, and characterization of the maltooligosyltrehalose trehalohydrolase from the thermophilic archaeon Sulfolobus solfataricus ATCC 35092

The maltooligosyltrehalose trehalohydrolase (MTHase) mainly cleaves the alpha-1,4-glucosidic linkage next to the alpha-1,1-linked terminal disaccharide of maltooligosyltrehalose to produce trehalose and the maltooligosaccharide with lower molecular mass. In this study, the treZ gene encoding MTHase was PCR-cloned from Sulfolobus solfataricus ATCC 35092 and then expressed in Escherichia coli. A high yield of the active wild-type MTHase, 13300 units/g of wet cells, was obtained in the absence of IPTG induction. Wild-type MTHase was purified sequentially using heat treatment, nucleic acid precipitation, and ion-exchange chromatography. The purified wild-type MTHase showed an apparent optimal pH of 5 and an optimal temperature at 85 degrees C. The enzyme was stable at pH values ranging from 3.5 to 11, and the activity was fully retained after a 2-h incubation at 45-85 degrees C. The k(cat) values of the enzyme for hydrolysis of maltooligosyltrehaloses with degree of polymerization (DP) 4-7 were 193, 1030, 1190, and 1230 s(-1), respectively, whereas the k(cat) values for glucose formation during hydrolysis of DP 4-7 maltooligosaccharides were 5.49, 17.7, 18.2, and 6.01 s(-1), respectively. The K(M) values of the enzyme for hydrolysis of DP 4-7 maltooligosyltrehaloses and those for maltooligosaccharides are similar at the same corresponding DPs. These results suggest that this MTHase could be used to produce trehalose at high temperatures.

[Purification and properties of isoflavone-glucosidase]

A high activity isoflavone-glucosidase, which hydrolysis glycosides, was obtainde using liquid fermentation from Absidia sp. R strain. The isoflavone-glucosidase was purified 11 folds with yielding rate of 10.9% after ammonium sulfate precipitation and DEAE-Cellocuse (DE-52) ion exchange chromatography. SDS-PAGE results showed that the molecular weight is 53kD. And the optimum temperature, the optimum pH, Km and pI of the enzyme are 50 deegrees C, 5.0, 1.3 x 10(-2) mol/L and 3.2, respectively. The isoflavone-glucosidase is also rather stable under 60 degrees C and in pH range from 5.0 to 7.0. The enzyme can be activated by Co2+ and Ca2+, and be inhibited by Ag+ and Cu2+.

Cloning and comparison of third beta-glucoside utilization (bglEFIA) operon with two operons of Pectobacterium carotovorum subsp. carotovorum LY34

A third bgl operon containing bglE, bglF, bglI, and bglA was isolated from Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34). The sequences of BglE, BglF, and Bgll were similar to those of the phosphotransferase system (PTS) components IIB, IIC, and IIA respectively. BglF contains important residues for the phosphotransferase system. The amino acid sequence of BglA showed high similarity to various 6-phospho-beta-glucosidases and to a member of glycosyl hydrolase family 1. Sequence and structural analysis also revealed that these four genes were organized in a putative operon that differed from two operons previously isolated from Pcc LY34, bglTPB (accession no. AY542524) and ascGFB (accession no. AY622309). The transcription regulator for this operon was not found, and the EII complexes for PTS were encoded separately by three genes (bglE, bglF, and bglI). The BglA enzyme had a molecular weight estimated to be 57,350 Da by SDS-PAGE. The purified beta-glucosidase hydrolyzed salicin, arbutin, rhoNPG, rhoNPbetaG6P, and MUG, exhibited maximal activity at pH 7.0 and 40 degrees C, and displayed enhanced activity in the presence of Mg2+ and Ca2+. Two glutamate residues (Glu178 and Glu378) were found to be essential for enzyme activity.

Heterologous expression, purification, crystallization and preliminary X-ray analysis of raucaffricine glucosidase, a plant enzyme specifically involved in Rauvolfia alkaloid biosynthesis

Raucaffricine glucosidase (RG) is an enzyme that is specifically involved in the biosynthesis of indole alkaloids from the plant Rauvolfia serpentina. After heterologous expression in Escherichia coli cells, crystals of RG were obtained by the hanging-drop vapour-diffusion technique at 293 K with 0.3 M ammonium sulfate, 0.1 M sodium acetate pH 4.6 buffer and 11% PEG 4000 as precipitant. Crystals belong to space group I222 and diffract to 2.30 A, with unit-cell parameters a = 102.8, b = 127.3, c = 215.8 A.

A two-stage refinement approach for the enhancement of excretory production of an exoglucanase from Escherichia coli

Hyper-expression of a secretory exoglucanase, Exg, encoded by the cex gene of Cellulomonas fimi was previously shown to saturate the SecYEG pathway and result in dramatic cell death of recombinant Escherichia coli (Z.B. Fu, K.L. Ng, T.L. Lam, W.K.R. Wong, Cell death caused by hyper-expression of a secretory exoglucanase in Esherichia coli, Protein Expr. Purif. 42 (2005) 67-77). We propose here that the cell lysate ratio (Pre/Mat RQ) of the unprocessed precursor Exg protein (Pre-Exg) and its processed mature product (Mat-Exg) reflects the capacity of E. coli to secrete Exg. A Pre/Mat RQ of 20/80, designated the "Critical Value," was an important threshold measurement. A rise in the Pre/Mat RQ triggered a mass killing effect. The use of various secretion signal peptides did not improve the viability of cells expressing high levels of Pre-Exg under strong tac promoter control. However, use of the weaker vegG promoter in conjunction with a change in start codon of the spa leader sequence from ATG to TTG in a pM1vegGcexL plasmid construct resulted in a high level (0.9 U ml(-1)) of excreted Exg in shake-flask cultures. This was 50% higher than the best result obtained from plasmid construct lacUV5par8cex, using the lacUV5 promoter and the ompA leader sequence. Variations in the excreted Exg activities were attributable to differences in the Pre/Mat RQ values of the induced cultures harboring pM1vegGcexL and lacUV5par8cex. These values were 18/82 and 10/90, respectively. Employing fed-batch cultivation in two-liter fermentors, an induced JM101(pM1vegGcexL) culture yielded 4.5 U ml(-1) of excreted Exg, which was over six fold greater that previously reported. Our results illustrate the successful application of the Pre/Mat RQ ratio as a guide to the attainment of a maximum level of secreted/excreted Exg.

Identification of maltooligosyltrehalose synthase and maltooligosyltrehalose trehalohydrolase enzymes catalysing trehalose biosynthesis in Anabaena 7120 exposed to NaCl stress

Anabaena 7120 cells were exposed to NaCl (25-175 mM) stress. Maximum growth was recorded in media containing 150mM NaCl. Short-term exposure (48h) of the cyanobacterial biomass to 150mM NaCl, induced highest trehalose level (37mM). Control cells lacking NaCl did not show any trace of trehalose as ascertained by NMR and HPLC analysis. Trehalose biosynthesis observed with NaCl plus high temperature (40 degrees C) indicated that its production was specifically triggered by NaCl, not temperature. The increase in trehalose level during NaCl stress was the result of overexpression of the trehalose-forming enzymes maltooligosyltrehalose synthase (MTSase), EC 5.4.99.15 (114kDa) and maltooligosyltrehalose trehalohydrolase (MTHase), EC 3.2.1.141 (68 kDa) as evidenced by SDS-PAGE analysis. To our knowledge this is the first report of induced trehalose biosynthesis in Anabaena 7120 during salt-stress, accompanied by identification of MTSase and MTHase enzymes on gel. It is suggested that Anabaena 7120 cells synthesize the osmolyte trehalose to withstand osmotic fluctuations.

Glycoprotein reglucosylation

Proteins following the secretory pathway acquire their proper tertiary and in certain cases also quaternary structures in the endoplasmic reticulum (ER). Incompletely folded species are retained in the ER and eventually degraded. One of the molecular mechanisms by which cells achieve this conformational sorting is based on monoglucosylated N-glycans (Glc1Man5-9GlcNAc2) present on nascent glycoproteins in the ER. This chapter discusses two of the steps that regulate the abundance of such N-glycan structures, including glycoprotein deglucosylation (by glucosidase II) and reglucosylation (by the UDP-Glc:glycoprotein glucosyltransferase), as well as an overview of methods to evaluate the N-glycans prevalent during glycoprotein biogenesis in the ER.

Production of a new sucrose derivative by transglycosylation of recombinant Sulfolobus shibatae β-glycosidase

The gene encoding beta-glycosidase of the hyperthermophilic archaea Sulfolobus shibatae (SSG) was expressed in Escherichia coli. Recombinant SSG (referred to as rSSG hereafter) was efficiently purified, and its transglycosylation activity was tested with lactose as a donor and various sugars as acceptors. When sucrose was used as an acceptor, we found a distinct intermolecular transglycosylation product and confirmed its presence by TLC and high performance anion exchange chromatography (HPAEC). The sucrose transglycosylation product was isolated by paper chromatography, and its chemical structure was determined by 1H and 13C NMR. The sucrose transfer product was determined to be beta-D-galactopyranosyl-(1-->6)-alpha-D-glucopyranosyl-beta-d-fructofuranoside with a galactose molecule linked to sucrose via a beta-(1-->6)-glycosidic bond.

Expression, purification, crystallization and preliminary X-ray analysis of strictosidine glucosidase, an enzyme initiating biosynthetic pathways to a unique diversity of indole alkaloid skeletons

Strictosidine beta-D-glucosidase, a plant enzyme initiating biosynthetic pathways to about 2000 monoterpenoid indole alkaloids with an extremely large number of various carbon skeletons, has been functionally expressed in Escherichia coli and purified to homogeneity in mg scale. Crystals suitable for X-ray analysis were found by robot-mediated screening. Using the hanging-drop technique, optimum conditions were 0.3 M ammonium sulfate, 0.1 M sodium acetate, pH 4.6 and PEG 4000 (10%) as precipitant buffer. The crystals of strictosidine glucosidase belong to the space group P42(1)2 with unit cell dimensions of a=157.63, c=103.59 A and diffract X-rays to 2.48-A resolution.

Sucrose hydrolases from the midgut of the sugarcane stalk borer Diatraea saccharalis

A beta-fructosidase (EC 3.2.1.26) was isolated from the midgut of larval sugar cane stalk borer Diatraea saccharalis by mild-denaturing electrophoresis and further purified to near homogeneity by gel filtration. beta-Fructosidase hydrolysed sucrose, raffinose and the fructosyl-trisaccharide isokestose, but it had no activity against maltose, melibiose and synthetic substrates for alpha-glucosidases. Two other sucrose hydrolases, one resembling a alpha-glucosidase (EC 3.2.1.20) and the other one active specifically against sucrose (sucrase) were detected in the larval midgut of D. saccharalis. All three sucrose hydrolases were associated with the midgut epithelium of larval D. saccharalis. Relative molecular mass (M(r)) of the beta-fructosidase was estimated around 45,000 (by gel filtration). The other two sucrose hydrolases had M(r) of 54,000 (alpha-glucosidase) and 59,000 (sucrase). The pH optima of the sucrose hydrolases were 5-10 for both alpha-glucosidase and sucrase and 7-8 for beta-fructosidase. Considering V(max)/K(m) ratios, beta-fructosidase preferentially cleaves isokestose rather than raffinose and sucrose. In order to evaluate the possible contribution of microorganisms isolated from the midgut to the pool of sucrose hydrolases, washed midgut epithelia were homogenised and plated onto appropriate media. Seven bacterial and one yeast species were isolated. None of the sucrose hydrolases extracted from the microorganisms corresponded to the enzymes isolated from midgut tissue homogenates. This result suggests that the major sucrose hydrolases found in the midgut of larval D. saccharalis were probably produced by the insect themselves not by the gut microflora.

Purification and characterization of an intracellular cycloalternan-degrading enzyme from Bacillus sp. NRRL B-21195

A novel intracellular cycloalternan-degrading enzyme (CADE) was purified to homogeneity from the cell pellet of Bacillus sp. NRRL B-21195. The enzyme has a molecular mass of 125 kDa on SDS-PAGE. The pH optimum was 7.0, and the enzyme was stable from pH 6.0 to 9.2. The temperature optimum was 35 degrees C and the enzyme exhibited stability up to 50 degrees C. The enzyme hydrolyzed cycloalternan [CA; cyclo(-->6)-alpha-d-Glcp-(1-->3)-alpha-d-Glcp-(1-->6)-alpha-d-Glcp-(-->3)-alpha-d-Glcp-(1-->)] as the best substrate, to produce only isomaltose via an intermediate, alpha-isomaltosyl-(1-->3)-isomaltose. This enzyme also hydrolyzed isomaltosyl substrates, such as panose, alpha-isomaltosyl-(1-->4)-maltooligosaccharides, alpha-isomaltosyl-(1-->3)-glucose, and alpha-isomaltosyl-(1-->3)-isomaltose to liberate isomaltose. Neither maltooligosaccharides nor isomaltooligosaccharides were hydrolyzed by the enzyme, indicating that CADE requires alpha-isomaltosyl residues connected with (1-->4)- or (1-->3)-linkages. The K(m) value of cycloalternan (1.68 mM) was 20% of that of panose (8.23 mM). The k(cat) value on panose (14.4s(-1)) was not significantly different from that of cycloalternan (10.8 s(-1)). Judging from its specificity, the systematic name of the enzyme should be cycloalternan isomaltosylhydrolase. This intracellular enzyme is apparently involved in the metabolism of starch via cycloalternan in Bacillus sp. NRRL B-21195, its role being to hydrolyze cycloalternan inside the cells.

Identification of aryl-phospho-?-d-glucosidases in Bacillus subtilis

Four aryl-phospho-beta- d-glucosidases were identified in Bacillus subtilis by using 4-methylumbelliferyl-phospho-beta- d-glucopyranoside as a substrate. Two of these enzymes are the products of the bglA and bglH genes, previously suggested to encode aryl-phospho-beta- d-glucosidases, while the other enzymes are encoded by the yckE and ydhP genes. Together, these four genes account for >99.9% of the glucosidase activity in B. subtilis on aryl-phospho-beta- d-glucosides. yckE was expressed at a low and constant level during growth, sporulation, and spore germination, and was not induced by aryl-beta- d-glucosides. ydhP was also not induced by aryl-beta- d-glucosides. However, while ydhP was expressed at only a very low level in exponential-phase cells and germinating spores, this gene was expressed at a higher levels upon entry into the stationary phase of growth. Strains lacking yckE or ydhP exhibited no defects in growth, sporulation, or spore germination or in growth on aryl-beta- d-glucosides. However, a strain lacking bglA, bglH and yckE grew poorly if at all on aryl-beta- d-glucosides as the sole carbon source.

Characterization of a beta-glycosidase highly active on disaccharides and of a beta-galactosidase from Tenebrio molitor midgut lumen

The midgut of the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae) larvae has four beta-glycosidases. The properties of two of these enzymes (betaGly1 and betaGly2) have been described elsewhere. In this paper, the characterization of the other two glycosidases (betaGly3 and betaGly4) is described. BetaGly3 has one active site, hydrolyzes disaccharides, cellodextrins, synthetic substrates and beta-glucosides produced by plants. The enzyme is inhibited by amygdalin, cellotriose, cellotetraose and cellopentaose in high concentrations, probably due to transglycosylation. betaGly3 hydrolyzes beta 1,4-glycosidic linkages with a catalytic rate independent of the substrate polymerization degree (k(int)) of 11.9 s(-1). Its active site is formed by four subsites, where subsites +1 and -1 bind glucose residues with higher affinity than subsite +2. The main role of betaGly3 seems to be disaccharide hydrolysis. BetaGly4 is a beta-galactosidase, since it has highest activity against beta-galactosides. It can also hydrolyze fucosides, but not glucosides, and has Triton X-100 as a non-essential activator (K(a)=15 microM, pH 4.5). betaGly4 has two active sites that can hydrolyze p-nitrophenyl beta-galactoside (NPbetaGal). The one hydrolyzing NPbetaGal with more efficiency is also active against methylumbellipheryl beta-D-galactoside and lactose. The other active site hydrolyzes NPbetaFucoside and binds NPbetaGal weakly. BetaGly4 hydrolyzes hydrophobic substrates with high catalytical efficiency and is able to bind octyl-beta-thiogalactoside in its active site with high affinity. The betaGly4 physiological role is supposed to be the hydrolysis of galactolipids that are found in membranes from vegetal tissues. As the enzyme has a hydrophobic site where Triton X-100 can bind, it might be activated by membrane lipids, thus becoming fully active only at the surface of cell membranes.

Cellobiose-6-phosphate hydrolase (CelF) of Escherichia coli: characterization and assignment to the unusual family 4 of glycosylhydrolases

The gene celF of the cryptic cel operon of Escherichia coli has been cloned, and the encoded 6-phospho-beta-glucosidase (cellobiose-6-phosphate [6P] hydrolase; CelF [EC 3.2.1.86]) has been expressed and purified in a catalytically active state. Among phospho-beta-glycosidases, CelF exhibits unique requirements for a divalent metal ion and NAD(+) for activity and, by sequence alignment, is assigned to family 4 of the glycosylhydrolase superfamily. CelF hydrolyzed a variety of P-beta-glucosides, including cellobiose-6P, salicin-6P, arbutin-6P, gentiobiose-6P, methyl-beta-glucoside-6P, and the chromogenic analog, p-nitrophenyl-beta-D-glucopyranoside-6P. In the absence of a metal ion and NAD(+), purified CelF was rapidly and irreversibly inactivated. The functional roles of the cofactors have not been established, but NAD(+) appears not to be a reactant and there is no evidence for reduction of the nucleotide during substrate cleavage. In solution, native CelF exists as a homotetramer (M(w), approximately 200,000) composed of noncovalently linked subunits, and this oligomeric structure is maintained independently of the presence or absence of a metal ion. The molecular weight of the CelF monomer (M(r), approximately 50,000), estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is in agreement with that calculated from the amino acid sequence of the polypeptide (450 residues; M(r) = 50,512). Comparative sequence alignments provide tentative identification of the NAD(+)-binding domain (residues 7 to 40) and catalytically important glutamyl residues (Glu(112) and Glu(356)) of CelF.

Purification and some properties of an Aspergillus niger beta-apiosidase from an enzyme preparation hydrolyzing aroma precursors

A beta-apiosidase was isolated and purified to electrophoretic homogeneity from an enzyme preparation, Klerzyme 200, through ammonium sulfate precipitation, gel filtration chromatography, ion-exchange chromatography, and HPLC on ion-exchange and size exclusion columns. The purification of the enzyme was aided by the synthesis of 4-methylumbelliferyl beta-D-apiofuranoside for the specific detection of activity on electrophoresis gels. The molecular mass estimated by SDS-PAGE was 120 kDa. The optimum activity of the beta-apiosidase was found at pH 5 and 40 degrees C. The K(m) and V(max) for p-nitrophenyl beta-D-apiofuranoside were 4.2 mM and 2460 nkat/mg of protein, respectively. The enzyme was not inhibited by glucose and ethanol. This enzyme hydrolyzed the intersugar linkages of apiofuranosylglucosides, aroma precursors from grape.

The gene bglH present in the bgl operon of Escherichia coli, responsible for uptake and fermentation of beta-glucosides encodes for a carbohydrate-specific outer membrane porin

The cryptic gene bglH from the Escherichia coli chromosome was cloned into a tacOP-driven expression vector. The resulting plasmid was transferred into the porin-deficient E. coli strain KS26 and the protein was expressed by addition of IPTG. The BglH protein was localized in the outer membrane. It was purified to homogeneity using standard methods. Reconstitution experiments with lipid bilayer membranes defined BglH as a channel-forming component, i.e. it is an outer membrane porin. The single-channel conductance of BglH (560 pS in 1 M KCl) was only one-third of that of the general diffusion porins of E. coli outer membrane. The presence of carbohydrates in the aqueous phase led to a dose-dependent block of ion transport through the channel, similar to that found for LamB (maltoporin) of E. coli and Salmonella typhimurium, which means that BglH is a porin specific for the uptake of carbohydrates. The binding constants of a variety of different carbohydrates were calculated from titration experiments of the BglH-induced membrane conductance. The tightest binding was observed with the aromatic beta-D-glucosides arbutin and salicin, and with gentibiose and cellobiose. Binding of maltooligosaccharides to BglH was in contrast to their binding to LamB in that it was much weaker, indicating that the binding site of BglH for carbohydrates is different from that of LamB (maltoporin). The kinetics of cellopentaose binding to BglH was investigated using the carbohydrate-induced current noise and was compared with that of cellopentaose binding to LamB (maltoporin) and ScrY (sucroseporin).

Cardenolide 16'-O-glucohydrolase from Digitalis lanata. Purification and characterization

A three-step chromatographic procedure was developed for purification of cardenolide 16'-O-glucohydrolase (CGH) from Digitalis lanata Ehrh. leaves, including Phenyl-Sepharose hydrophobic interaction chromatography followed by SP-Sepharose cation exchange and Q-Sepharose anion-exchange chromatography. Starting with acetone dry powder the purification resulted in an 760-fold enrichment of CGH. Molecular weight, substrate specificity, pH optimum and temperature stability of CGH were determined. Antibodies against CGH were prepared in rabbits. The SDS gel electrophoresis of protein extracts from leaves of D. lanata and other D. species showed bands at 70 kDa and 36 kDa reacting with the antibodies. The 70-kDa protein is the main protein stained with CGH antibodies in freshly prepared extracts of D. lanata. It may represent undegraded CGH. The 36-kDa protein is enriched in aged CGH preparations. It is probably a degradation product. Proteins related to 70-kDa and 36-kDa bands also occur in crude protein preparations from leaves of D. heywoodii P. et M. Silva, D. mariana Boiss., D. purpurea L., and D. thapsi L. indicating that CGH is also present in these species. Purified CGH was digested with proteases V8 and Lys-C and the resulting fragments obtained were sequenced. One fragment had the typical amino-acid sequence of the catalytic center of family-1 glycosyl hydrolases (EC 3.2.1.x). Cardenolide 16'-O-glucohydrolase, like the other members of this enzyme family, appeared to have a glutamic acid residue directly involved in glycosidic bond cleavage as a nucleophile.

Enzymes responsible for the metabolism of saikosaponins from Eubacterium sp. A-44, a human intestinal anaerobe

From a human intestinal bacterium, Eubacterium sp. A-44, which is capable of hydrolyzing saikosaponins to saikogenins, two glycosidases, beta-D-glucosidase and a novel type of beta-D-fucosidase, were isolated and characterized as saikosaponin-hydrolyzing beta-D-glucosidase and prosaikogenin-hydrolyzing beta-D-fucosidase. Relative to the hydrolyzing activities toward saikosaponins a, b1 and b2, the beta-D-glucosidase showed lower ability to hydrolyze saikosaponin d, but no ability to hydrolyze saikosaponin c or prosaikogenins. By Sephacryl S-300 column chromatography, the molecular weight of prosaikogenin-hydrolyzing beta-D-fucosidase was estimated to be about 130 kDa. The beta-D-fucosidase could hydrolyze prosaikogenins A and F, but not prosaikogenins D and G or saikosaponins. Relative to p-nitrophenyl beta-D-fucoside-hydrolyzing activity, this enzyme had 32.0% and 22.2% of its hydrolyzing ability toward p-nitrophenyl beta-D-glucoside and p-nitrophenyl beta-D-galactoside, respectively. p-Nitrophenyl beta-D-fucoside-hydrolyzing activity was inhibited by D-fucose, and was weakly inhibited by D-glucose, D-glucono delta-lactone, D-galactose and D-galactono delta-lactone. By combining these two glycosidases, saikosaponins a and b1 were converted to their saikogenins via the corresponding prosaikogenins.

Phospho-beta-glucosidase from Fusobacterium mortiferum: purification, cloning, and inactivation by 6-phosphoglucono-delta-lactone

6-Phosphoryl-beta-D-glucopyranosyl:6-phosphoglucohydrolase (P-beta-glucosidase, EC 3.2.1.86) has been purified from Fusobacterium mortiferum. Assays for enzyme activity and results from Western immunoblots showed that P-beta-glucosidase (Mr, 53,000; pI, 4.5) was induced by growth of F. mortiferum on beta-glucosides. The novel chromogenic and fluorogenic substrates, p-nitrophenyl-beta-D-glucopyranoside-6-phosphate (pNPbetaGlc6P) and 4-methylumbelliferyl-beta-D-glucopyranoside-6-phosphate (4MUbetaGlc6P), respectively, were used for the assay of P-beta-glucosidase activity. The enzyme hydrolyzed several P-beta-glucosides, including the isomeric disaccharide phosphates cellobiose-6-phosphate, gentiobiose-6-phosphate, sophorose-6-phosphate, and laminaribiose-6-phosphate, to yield glucose-6-phosphate and appropriate aglycons. The kinetic parameters for each substrate are reported. P-beta-glucosidase from F. mortiferum was inactivated by 6-phosphoglucono-delta-lactone (P-glucono-delta-lactone) derived via oxidation of glucose 6-phosphate. The pbgA gene that encodes P-beta-glucosidase from F. mortiferum has been cloned and sequenced. The first 42 residues deduced from the nucleotide sequence matched those determined for the N terminus by automated Edman degradation of the purified enzyme. From the predicted sequence of 466 amino acids, two catalytically important glutamyl residues have been identified. Comparative alignment of the amino acid sequences of P-beta-glucosidase from Escherichia coli and F. mortiferum indicates potential binding sites for the inhibitory P-glucono-delta-lactone to the enzyme from F. mortiferum.

The role of the cellulolytic high molecular mass (HMM) complex of the anaerobic fungus Piromyces sp. strain E2 in the hydrolysis of microcrystalline cellulose

The anaerobic fungus Piromyces sp. strain E2 produces extracellular cellulolytic enzymes present both in a high molecular mass (HMM) complex or as individual proteins. Although the HMM complex was present in the culture fluid during all growth stages, the highest amounts of complex were obtained when cultures were harvested at the end of fungal growth. The complex obtained after gel-filtration chromatography on Sephacryl S-300 HR was found to be the major factor in hydrolysis of cellulose to glucose (sole product, up to 250 mM). The complex was very stable as demonstrated by identical hydrolysis patterns with fresh preparations or preparations stored at 4 degrees C for 2 months. From inhibition experiments with gluconic acid lactone and glucose, it was concluded that the HMM complex must contain at least one glucohydrolase. SDS-PAGE analysis revealed that a partially purified HMM complex was composed of at least ten polypeptides and contained numerous endoglucanases and one beta-glucosidase.

Purification and characterization of thermostable maltooligosyl trehalose trehalohydrolase from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius

A thermostable maltooligosyl trehalose trehalohydrolase from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius ATCC 33909 was purified from a cell-free extract to an electrophoretically pure state by successive column chromatographies on Sepabeads FP-DA13, Butyl-Toyopearl 650M, DEAE-Toyopearl 650S, Toyopearl HW-55S and Ultrogel AcA44. The enzyme had a molecular mass of 59,000 by SDS-polyacrylamide gel electrophoresis and a pI of 6.1 by gel isoelectrofocusing. The N-terminal amino acid of the enzyme was methionine. The enzyme showed the highest activity from pH 5.5 to 6.0 and at 75 degrees C, and was stable from pH 5.5 to 9.5 and up to 85 degrees C. The activity was inhibited by Hg2+, Cu2+, Fe2+, Pb2+, and Zn2+. The Km values of the enzyme for maltosyl trehalose, maltotriosyl trehalose, maltotetraosyl trehalose, and maltopentaosyl trehalose were 16.7 mM, 2.7 mM, 3.7 mM, and 4.9 mM, respectively.

Isozyme polymorphism of cellulases in Aspergillus terreus

Maximum cellulase production in Aspergillus terreus was obtained at a temperature of 28 degrees C, pH 4.0 and a substrate concentration of 1% CMC. Variability in cellulase enzyme production and isozyme polymorphism of endo-beta-1,4-glucanase and beta-1,4-glucosidase was studied in 45 natural isolates of A. terreus. Different electrophoretic patterns were evident for endoglucanase. Three zones of activity viz EG 1, EG 11 and EG 111 were observed showing different electrophoretic mobilities. Some of the isolates exhibited the presence of null alleles for EG 1. During development EG 1 and EG 11 were observed throughout while EG 111 appeared on the eighth day. For beta-1,4-glucosidase two zones of activity viz beta-glu 1 and beta-glu 11 were observed. beta-glu 1 showed variable electrophoretic mobilities. beta-glu 1 appeared throughout during development while beta-glu 11 appeared on the twelfth day.

Purification and characterization of a novel enzyme, maltooligosyl trehalose trehalohydrolase, from Arthrobacter sp. Q36

A novel enzyme, maltooligosyl trehalose trehalohydrolase from Arthrobacter sp. Q36 was purified from a cell-free extract to an electrophoretically pure state by successive column chromatography on Sepabeads FP-DA13, Butyl-Toyopearl 650M, DEAE-Toyopearl 650S, and Toyopearl HW-55S. The enzyme specifically catalyzed the hydrolysis of the alpha-1,4-glucosidic linkage that bound the maltooligosyl and trehalose moieties of maltooligosyl trehalose. The Km of the enzyme for maltosyl trehalose, maltotriosyl trehalose, maltotetraosyl trehalose, and maltopentaosyl trehalose was 5.5 mM, 4.6 mM, 7.0 mM, and 4.2 mM, respectively. The enzyme had a molecular mass of 62,000 by SDS-polyacrylamide gel electrophoresis and a pI of 4.1 by gel isoelectrofocusing. The N-terminal amino acid of the enzyme was threonine. The enzyme showed the highest activity at pH 6.5 and 45 degrees C, and was stable from pH 5.0 to 10.0 and up to 45 degrees C. The activity was inhibited by Hg2+, Cu2+, Fe2+, and Zn2+.

Potential of genes and gene products from Trichoderma sp. and Gliocladium sp. for the development of biological pesticides

Fungal cell wall degrading enzymes produced by the biocontrol fungi Trichoderma harzianum and Gliocladium virens are strong inhibitors of spore germination and hyphal elongation of a number of phytopathogenic fungi. The purified enzymes include chitinolytic enzymes with different modes of action or different substrate specificity and glucanolytic enzymes with exo-activity. A variety of synergistic interactions were found when different enzymes were combined or associated with biotic or abiotic antifungal agents. The levels of inhibition obtained by using enzyme combinations were, in some cases, comparable with commercial fungicides. Moreover, the antifungal interaction between enzymes and common fungicides allowed the reduction of the chemical doses up to 200-fold. Chitinolytic and glucanolytic enzymes from T. harzianum were able to improve substantially the antifungal ability of a biocontrol strain of Enterobacter cloacae. DNA fragments containing genes encoding for different chitinolytic enzymes were isolated from a cDNA library of T. harzianum and cloned for mechanistic studies and biocontrol purposes. Our results provide additional information on the role of lytic enzymes in processes of biocontrol and strongly suggest the use of lytic enzymes and their genes for biological control of plant diseases.

A new enzyme, maltobionate alpha-D-glucohydrolase, from alkalophilic Bacillus sp. N-1053

A new enzyme, maltobionate alpha-D-glucohydrolase, was purified to apparent homogeneity from a cell-free extract of alkalophilic Bacillus sp. N-1053 about 930-fold with a yield of 18% and some of its properties were investigated. The enzyme showed optimum activity at about pH 7.0, and was stable over the range of pH 6.0-9.5. The molecular weight was estimated to be 152,000 and 71,000 by HPLC gel filtration on TSKgel G3000SWXL and SDS-polyacrylamide gel electrophoresis, respectively. The enzyme hydrolyzed maltobionate more effectively than disaccharides such as maltose and maltitol or trisaccharides such as maltotrionate, maltotriose and maltotriitol, but showed no activity toward polysaccharides such as amylose, amylopectin and soluble starch. The reaction products from 1 mol of maltobionate were found to be 1 mol of beta-D-glucose and 1 mol of D-gluconate. The Km value for maltobionate was 1.63 mM and the Vmax/Km value for maltobionate was the largest among the substrates tested. The enzyme activity was almost completely inhibited by Hg2+, Ag+, iodine and N-bromosuccinimide, and also inhibited by p-nitrophenyl alpha-D-glucoside, maltose and maltitol.

Purification and characterization of a Bacillus sp. SAM1606 thermostable alpha-glucosidase with transglucosylation activity

We purified a novel alpha-glucosidase to homogeneity from an Escherichia coli recombinant transformed with the alpha-glucosidase gene from thermophilic Bacillus sp. SAM1606. The enzyme existed as mono- and multimeric forms of a promoter protein with a relative molecular weight of 64,000 and isoelectric point of 4.6. We isolated a monomeric form of the enzyme and characterized it. The enzyme was unique among the known alpha-glucosidases in both broad substrate specificity and high thermostability. The enzyme hydrolysed a variety of O-alpha-D-glucopyranosides such as nigerose, maltose, isomaltose, sucrose, and trehalose efficiently. The molecular activity (k0) and the Michaelis constant (Km) values at 55 degrees C and pH 6.0 for sucrose were 54.6 s-1 and 5.3 mM, respectively. The optimum pH and temperature for hydrolysis were pH 5.5 and 75 degrees C, respectively. The enzyme exhibited a high transglucosylation activity: it reacted with 1.8 M sucrose at 60 degrees C for 70 h to yield oligosaccharides containing theanderose in a maximum yield of 35% (w/w). High thermostability of the enzyme (stable up to 65 degrees C at pH 7.2 for 10 min) permits the transglucosylation reaction at high temperatures, which would be beneficial for continuous production of oligosaccharides from sucrose.

Molecular cloning of the extracellular endodextranase of Streptococcus salivarius

We report the cloning in Escherichia coli of the gene encoding an extracellular endodextranase (alpha-1,6-glucanhydrolase, EC 3.2.1.11) from Streptococcus salivarius PC-1. Recombinants from a S. salivarius PC-1-Lambda ZAP II genomic library specifying dextranase activity were identified as plaques surrounded by zones of clearing on blue dextran agar. One such clone, PD1, had a 6.3-kb EcoRI fragment insert which encoded a 190-kDa protein with dextranase activity. The recombinant strain also produced two lower-molecular-mass polypeptides (90 and 70 kDa) that had dextranase activity. Native dextranase was recovered from concentrated culture fluids of S. salivarius as a single 110-kDa polypeptide. PD1 phage lysate and PC-1 culture supernatant fluid extract were used to measure substrate specificity of the recombinant and native forms of dextranase, respectively. Analysis of these reaction products by thin-layer chromatography revealed the expected isomaltosaccharide products yielded by the recombinant-specified enzyme but was unable to resolve the larger polysaccharide products of the native enzyme. Furthermore, S. salivarius utilized neither the substrates nor the products of dextran hydrolysis for growth.

Recovery of biologically active enzymes after HPLC separation

The mass and activity recovery of eight different enzymes (two monomeric, six oligomeric) with molecular masses between 25,000 and 240,000 daltons were tested after HPLC separation on three different HPLC instruments (two with stainless steel and one with titanium flow paths). Most of the tested proteins are known to be sensitive to heavy metal ions. Eight wide pore, ion-exchange columns, two size-exclusion columns and two hydrophobic-interaction columns were used. Both stainless steel and glass column hardware were used in all three separation modes. The elution times were between 8 and 12 minutes. In almost all cases, the activity recovery was between 90% and 100% compared with a control sample incubated in the chromatographic elution buffer for the same time at the same temperature. A severe activity loss (about 30%) was observed with only one ion-exchange column and one enzyme. Neither the column hardware nor the material of the HPLC equipment had any negative effect on the activity recovery of the enzymes tested.

Fractionation of renal brush border membrane proteins with Triton X-114 phase partitioning

Analysis of brush border membrane proteins by gel electrophoresis has revealed a complex polypeptide composition. We have investigated the use of Triton X-114 phase partitioning to fractionate such proteins on the basis of their degree of hydrophobicity. Each of the fractions was composed of a complex but distinct set of proteins. Most proteins were solubilized by Triton X-114 and partitioned into the detergent-poor fraction. Trehalase, gamma-glutamyl transpeptidase, and leucine aminopeptidase were well solubilized (greater than 80%) and enriched 5.1-, 3.9-, and 2.5-fold in the detergent-rich fraction. In contrast, alkaline phosphatase and 5'-nucleotidase were poorly solubilized. The specific activities of these enzymes were increased 2.7- and 2.3-fold in the insoluble protein fraction. Maltase was almost completely solubilized and partitioned into the detergent-poor fraction with a small enrichment factor (1.3). These results suggest that Triton X-114 phase partitioning could be useful as a first step in the purification of many brush border membrane proteins.

Purification and properties of a beta-glucosidase from Penicillium oxalicum autolysates

A beta-glucosidase from the medium of an autolyzed culture of Penicillium oxalicum has been purified by tannic acid precipitation, sephacryl S-200, DEAE-Biogel, CM-Biogel and Mono Q successively. The purification process produced a homogeneous band in the SDS-PAGE that correspond to a Mr of 133,500. The enzyme had a pl of 4, and the active optima were found at pH 5.5 and 55 degrees C. The enzyme hydrolyzed different substrates showing maximum affinity against p-nitrophenyl-beta-D-glucoside with a Km value of 0.37 mM. The beta-glucosidase was inhibited by Glucono-D-lactone but not by glucose in the concentration range of 1 to 10 mM. The enzyme was adsorbed by Concanavalin-A-Sepharose.

Purification and characterization of cellulolytic enzymes produced by Aspergillus nidulans

Three exo-glucanases, two endo-glucanases and two beta-glucosidases were separated and purified from the culture medium of Aspergillus nidulans. The optimal assay conditions for all forms of cellulase components ranged from pH 5.0 to 6.0 and 50 degrees C and 65 degrees C for exo-glucanases and endo-glucanases but 35 degrees C and 65 degrees C for beta-glucosidases. A close relation of enzyme stability to their optimal pH range was observed. All the cellulase components were stable for 10 min at 40-50 degrees C. Exo-II and Exo-III (Km, 38.46 and 37.71 mg/ml) had greater affinity for the substrate than Exo-I (Km, 50.00 mg/ml). The Km values of Endo-I and Endo-II (5.0 and 4.0 mg/ml) and their maximum reaction velocities (Vmax, 12.0 and 10.0 IU/mg protein) were comparable. beta-Glucosidases exhibited Km values of 0.24 and 0.12 mmol and Vmax values of 8.00 and 0.67 IU/mg protein. The molecular weights recorded for various enzyme forms were: Exo-I, 29,000; Exo-II, 72,500; Exo-III, 138,000; Endo-I, 25,000; Endo-II, 32,500; beta-Gluco-I, 14,000 and beta-Gluco-II, 26,000. Exo- and endo-glucanases were found to require some metal ions as co-factors for their catalytic activities whereas beta-glucosidases did not. Hg2+ inhibited the activity of all the cellulase components. The saccharification studies demonstrated a high degree of synergism among all the three cellulase components for hydrolysis of dewaxed cotton.

Purification of xylanase, beta-glucosidase, endocellulase, and exocellulase from a thermophilic fungus, Thermoascus aurantiacus

A strain of thermophilic fungus, Thermoascus aurantiacus, was isolated from local soil. From the culture filtrates of the organism grown on blotting paper, a xylanase, beta-glucosidase, exocellulase, and endocellulase were obtained in large amounts in highly purified form by employing ion-exchange and gel-permeation chromatography. The xylanase was crystallized. The xylanase and endocellulase were stable at 70 degrees C for 8 h, whereas the beta-glucosidase and exocellulase were less stable at 70 degrees C.

Human intestinal lactase-phlorizin hydrolase: isolation and preparation of a specific antiserum

Human intestinal lactase-phlorizin hydrolase (lactase) was selectively isolated with monospecific polyclonal antibodies to rat lactase. In addition to their immunologic similarities indicated by this isolation, human and rat lactase have similar kinetic characteristics but different subunit structure when analyzed by gel electrophoresis under reducing conditions. Rabbits immunized by injecting human lactase complexed with anti-rat lactase produced specific antibodies to human lactase that exhibited little cross-reactivity to the rat enzyme. The simple single-step procedure allows isolation of human lactase in high purity from small biologic samples and preparation of specific antisera to the human enzyme.

[Purification and properties of beta-glucosidase from Aspergillus phoenicis]

A beta-glucosidase has been purified to electrophoretically homogeneity from the wheat bran culture of Aspergillus phoenicis by PEG 6000-phosphate biphasic separation, column chromatography on Sephadex G-100, DEAE-Sephadex A-50 and SE-Sephadex C-50. The enzyme showed optimal activity at pH 5.0 and 60 degrees C. It was stable in the pH range of 4.0-7.5 and up to 55 degrees C. The enzyme activity was strongly inhibited by Ag+ and Hg2+. The molecular weight of the enzyme was 118000 as determined by SDS-PAGE and 195000 by gradient-PAGE. The isoelectric point was pI 3.95 as determined by PAGIF.

Purification of lysosomal membrane-bound glucocerebrosidase from human cultured fibroblasts using high-performance liquid chromatography

Glucocerebrosidase from human skin fibroblasts was purified more than 2300-fold to apparent homogeneity with an overall yield of 39% using taurocholate extraction, ammonium sulfate fractionation, and high-performance hydrophobic interaction and gel permeation column chromatography. This relatively high yield is attributed to two modifications from previously published procedures: (i) the elimination of a butanol delipidation step that resulted in substantial loss of enzyme activity; and (ii) the use of 2% (w/v) sodium taurocholate instead of 1-2% sodium cholate that resulted in more than 90% solubilization of total membrane-bound enzyme activity. Confluent monolayers of human cultured skin fibroblasts (approximately 3.6 x 10(8) cells) were harvested from 10 roller bottles. Glucocerebrosidase in the cell pellet was solubilized with 2% (w/v) sodium taurocholate, fractionated in 14% ammonium sulfate, and applied to a high-performance hydrophobic interaction phenyl-5PW column. After an ammonium sulfate descending linear gradient step, glucocerebrosidase was eluted from the column at 4% cholate concentration using a 0-5% linear cholate gradient. There was a 36-fold purification and 80% recovery. In the subsequent step, concentrated glucocerebrosidase fractions from the phenyl column were injected into two Bio-Sil TSK-250 gel permeation columns joined in series. Glucocerebrosidase peak activity was eluted at 263 ml corresponding to Mr 76,000. There was an 18-fold purification and 78% recovery. The enzyme preparation was then recycled through the phenyl-5PW column in order to remove a remaining contaminant.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial purification and characterization of alpha-glucosidase from Rothia dentocariosa

Disaccharidases of oral bacteria, especially alpha-glucosidase and beta-fructofuranosidase, are considered to play an important role in the induction of dental caries. Upon the examination of disaccharidases from several strains of saccharolytic oral bacteria, we found all of those bacteria to be capable of hydrolyzing the glycosidic linkage of sucrose. One species of bacteria, Rothia dentocariosa, was found to contain a single disaccharidase, alpha-glucosidase. This enzyme was partially purified by ammonium sulfate precipitation, gel filtration and ion-exchange column chromatography. The optimum pH and temperature for the enzyme activity was found to be 6.8-7.0 and 40 degrees C, respectively. The enzyme activity was strongly inhibited by Ag+, Hg2+, Cu2+, Fe2+ and Tris (Hydroxymethyl) aminomethane.

Purification and some properties of Candida albicans exo-1,3-beta-glucanase

An exo-1,3-beta-glucanase was purified from blastoconidia of Candida albicans 1001. The purified enzyme appeared as a single protein band by PAGE, and split into two subunits (Mr approximately 63,000 and 44,000) when analysed by SDS-PAGE. The pI of the enzyme was 4 and a Km of 1.7 mg ml-1 was estimated for laminarin as substrate. Despite its very reduced activity on the synthetic substrate p-nitrophenyl beta-D-glucoside, C. albicans exo-1,3-beta-glucanase hydrolysed 1,3-beta-glucan by an exo-splitting mechanism and was inhibited by glucono-delta-lactone and by Hg2+ and Ag+ cations. The active exo-glucanase was mainly located in the periplasm, but it was also present inside the cytoplasmic membrane in small amounts and was secreted into the culture medium. The electrophoretic mobility of the enzyme from all three locations was the same.

Purification and characterization of a broad specificity beta-glucosidase from sheep liver

1. A soluble beta-glucosidase from sheep liver has been isolated and purified 114-fold by conventional enzyme fractionation procedures. The specific activity of the purified enzyme was 5910 mU/mg of protein. 2. The enzyme has a broad specificity and hydrolyzes the p-nitrophenyl derivatives of beta-D-glucose, beta-D-galactose, beta-D-fucose, beta-D-xylose and alpha-L-arabinose. The best Vmax/Km value corresponds to the beta-glucosidase activity. 3. The enzyme has a pH optimum between 4.5-5.5 for all the activities, and mol. wt 95,000. 4. A variety of chemicals was tested as possible activators or inhibitors. 5. The enzyme is strongly inhibited by aldono 1-5 lactones and DMDP. 6. The kinetic evidences suggest a substrate activation model and the existence of two active sites (a "gluco-fuco" site and a "galacto" site). 7. The activation energies were calculated from beta-glucosidase and beta-galactosidase activities.

Purification and properties of the beta-glucosidase from a nitrile hydratase-producing Brevibacterium sp. strain R312

Besides its nitrile hydratase and wide spectrum amidase activities, the Brevibacterium sp. R312 strain also possesses a constitutive beta-glucosidase. Its optimum pH is 6. The enzyme was purified by fractionation precipitation with ammonium sulfate followed by chromatographic elutions on Q-Sepharose Fast Flow, Sephadex G-200 and Phenyl Superose. The resulting purification was 1960 folds for a 6% yield. The molecular weight of this enzyme was estimated at 180,000. It contains two identical sub-units. The pI is 5.5. This enzyme has a strong affinity for aryl-beta-glycosides:pNPG, prunassine; it could also degrade linamarine. It is inhibited by p-chloromercuribenzoate, delta-gluconolactone and glucose.

An M(III)-facilitated flocculation technique for enzyme recovery and concentration

An inexpensive and rapid flocculation/dissolution technique based upon Al(III) or Fe(III) was shown to be effective in recovering and concentrating up to 84% of the active enzyme from two dilute enzyme systems. The enzymes, a protease (Caldolysin) and a beta-glucosidase, were precipitated at constant pH and ambient temperature by addition of Fe(III) or Al(III) solutions. Resulting colloidal hydrous oxide particles bound the enzymes enabling subsequent separation from the media by low speed centrifugation. The enzymes were recovered from the protein/M(III) precipitate by complexing the M(III) with citrate. A concentration factor of 94 was obtained for the beta-glucosidase system when the initial concentration was less than 1 mg.ml-1.

Design of enzyme systems for selective product release from microbial cells; isolation of a recombinant protein from yeast

The development of expression systems for recombinant proteins and recombinant protein particles that cannot be secreted and that are located in specific cell locations necessitates the development of novel, more selective, techniques for cell disruption. Mechanical cell disruption methods do not discriminate the release of the desired product from among a host of other contaminating molecules and cell debris, and they also may damage the protein product. In contrast, the use of lytic enzyme systems, which can provide biological specificity to the process of cell lysis and disruption, shows an interesting potential for controlled lysis. In this report, the design and the use of lytic enzyme systems for differential product release from microbial cells have been reviewed. Lytic enzyme systems are usually specific either for yeast or for different types of bacteria. Moreover, the activity profile of a lytic system will have an effect on the product distribution. This profile can be manipulated at the genetic, physiological, production reactor, enzyme purification, and lysis reactor levels. Alternative process designs that will allow the sequential release of products from different cell locations have been reviewed and discussed. Alternatives have been explored by process modeling, process simulation, and optimization techniques. These studies show that the use of lytic enzyme systems has tremendous promise as a method of controlled lysis and differential product release. Finally, the release of a specific recombinant protein, human serum albumin (HSA) from yeast cells, has been investigated. The low levels of wall-lytic protease present in the Oerskovia lytic enzyme system have no deleterious effect on the protein product, and the level of HSA extracted from two positive yeast clones using lytic enzymes is similar to that extracted after bead breakage.

Purification of the beta-glucosidase from Sclerotinia sclerotiorum

A beta-glucosidase (EC 3.2.1.21) has been isolated from culture filtrates of the fungus Sclerotinia sclerotiorum. The protein was purified by gel filtration on a column of Bio-Gel P-300 and by ion exchange chromatography on DEAE-Bio-Gel A. The molecular weight, determined by gel filtration, was 240,000. Km values for the enzyme towards p-nitrophenyl-beta-D-glucoside and cellobiose were respectively 0.10 mM and 1.23 mM. The beta-glucosidase activity was found to be strongly associated with a beta-xylosidase (EC 3.2.1.37) activity, suggesting that both activities could be represented in a single protein complex.

Characterization of cyanogenic beta-glucosidase (linamarase) from cassava (Manihot esculenta Crantz)

Linamarase (EC 3.2.1.21) was purified from cassava petiole, stem, and root cortex by ammonium sulfate precipitation, column chromatography on Sepharose 6B, and chromatofocusing. The last step resolved the enzyme from each source into three forms with pI values of 4.3, 3.3, and 2.9. Each form was found to be oligomeric, consisting of one kind of subunit, Mr 63,000. The major isozyme with a pI of 4.3 from petiole showed a Km for linamarin of 0.6 mM and possessed both beta-glucosidase and beta-fucosidase activities. The former was sensitive to inhibition by delta-gluconolactone, isopropyl-beta-D-thioglucoside, and HgCl2, whereas the latter was inhibited by Tris ion.

Purification and characterization of a beta-glucosidase from Evernia prunastri

Intracellular beta-glucosidase from Evernia prunastri has been purified to homogeneity using anion exchange on DEAE-Sephadex A-50, and gel filtration chromatography on Sephadex G-100 and Sepharose 6B. The purified beta-glucosidase showed a single protein band on native electrophoresis and its isoelectric point was at pH 3.12. The molecular mass, calculated from its partition coefficient on the Sepharose 6B column, was 311 kDa, being composed of several subunits of 60 and 70 kDa. The highest activity of this enzyme was attained at pH 4.0 and 60 degrees C. The enzyme showed strong resistance to thermal inactivation. Its activation energy was about 15 kJ/mol. Cellobiose, salicin, and p-nitrophenyl beta-D-glucoside, but not carboxymethylcellulose, were hydrolyzed by the enzyme, following substrate inhibition kinetics. The purified beta-glucosidase was considered a true cellobiase because of its great affinity towards cellobiose. Cellobiose inhibition does not seem to be a physiological phenomenon. Glucose inhibited enzyme activity in a competitive way (Ki = 1.26 mM). Fe3+ and Co2+ inhibited activity notably. Hg2+, Cu2+ and EDTA were practically ineffective. Even 200 mM gluconolactone did not affect enzyme activity.

Solubilization of membrane-bound acid alpha-glucosidase by proteolysis

The membrane-bound acid alpha-glucosidase was purified partially (400-fold) from human placenta by solubilization with trypsin, concanavalin A-Sepharose chromatography, Ultrogel AcA-34 gel filtration, and Sephadex G-100 affinity chromatography. Two molecular forms of the enzyme were found in the final preparation of the purified enzyme. They were identical in molecular weight with a precursor (110 kDa) and an early intermediate form (105 kDa) of this enzyme. Also direct incubation of the membrane fraction without trypsin resulted in a release mainly of the 105 kDa form, which was inhibited by N-ethylmaleimide, but not by leupeptin, pepstatin or phenylmethylsulfonylfluoride. It was concluded that the precursor of acid alpha-glucosidase is an intrinsic membrane protein, which is transported into lysosomes after solubilization by proteolysis.

Isolation of a cytosolic beta-glucosidase from calf liver and characterization of its active site with alkyl glucosides and basic glycosyl derivatives

A beta-glucosidase/beta-galactosidase with Mr 52,500 was isolated from calf liver cytosol by a four-step procedure incorporating affinity chromatography on N-(9-carboxynonyl)-deoxynojirimycin-AH-Sepharose. Its pH optimum was at 5.8 with half-maximal activity at pH 3.5 and 8.6. Affinity for gluco compounds expressed by Km or Ki of substrates and inhibitors was 2- to 10-fold higher than for the corresponding galacto compounds. Alkyl glucosides were hydrolyzed with lower Vmax than p-nitrophenyl and 4-methylumbelliferyl glucosides, but due to their higher affinity the alkyl glucosides displayed values for kcat/Km of the same magnitude of the aryl glucosides when the alkyl chains were longer than octyl. Glucosylsphingosine was bound with Ki (= Km) 2.2 microM and hydrolyzed with a Vmax that was 50-fold lower than the Vmax for 4-methylumbelliferyl beta-glucoside. The product sphingosine was inhibitory with Ki 0.30 microM. A systematic study with alkyl glucosides and glucosylamines defined the aglycon site as a narrow, strongly hydrophobic cleft able to accommodate up to 10 methylene groups. Each CH2 group contributed 3.1 kJ/mol to the standard free energy of binding. The inhibition by gluco- and galactosylamine and by 1-deoxynojirimycin and its D-galacto analog was approximately 200-fold better than by corresponding nonbasic compounds. pH dependence of the inhibition and comparison with permanently cationic glycosyl derivatives showed that the nonprotonated form was the inhibiting species. This feature puts the cytosolic beta-glucosidase in the large class of glycoside hydrolases which strongly bind basic glycosyl derivatives by their protonation at the active site and formation of a shielded ion pair with the carboxylate of an aspartic or glutamic side chain.