Simple, high-yield purification of xanthine oxidase from bovine milk.

Xanthine oxidase, a commercially important enzyme with a wide area of application, was extracted from fresh milk, without added preservatives, using toluene and heat. The short purification procedure, with high yield, consisted of extraction, ammonium sulfate fractionation, and DEAE-Sepharose (fast flow) column chromatography. Xanthine oxidase was eluted as a single activity peak from the column using a buffer gradient. The purification fold, specific activity and yield for the purified xanthine oxidase were 328, 10.161 U/mg and 69%, respectively. The enzyme was concentrated by ultrafiltration, although 31% of the activity was lost during concentration, no change in specific activity was observed. Activity and protein gave coincident staining bands on native polyacrylamide gels. The intensity and the number of bands were dependent on the oxidative state(s) of the enzyme; reduction by 2-mercaptoethanol decreased the intensity of the slow-moving bands and increased the intensity of the fastest-moving band. Following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two major bands (molecular masses of 152 and 131 kDa) were observed, accounting for > or = 95% of xanthine oxidase. Native- and SDS-PAGE showed that the purified xanthine oxidase becomes a heterodimer due to endogenous proteases.     

Interactions of dextransucrase purified from Streptococcus mutans 890 with plant polyphenols

Plant polyphenols have been extensively studied for their chemopreventive properties for human health. Dextransucrase plays an essential role in synthesizing exopolysaccharides from its exclusive substrate sucrose in Streptococcus mutans. In the present study, the effect of polyphenols gallic acid and tannic acid was investigated on the dextransucrase activity. The enzyme was purified by ethanol precipitation followed by column chromatography by Sephadex G-200 gel chromatography, followed by PEG-400 treatment. The purified enzyme exhibited 52 fold enrichment with 17.5% yield and specific activity of 3.54 Units/mg protein. On SDS-PAGE enzyme protein gave a single band with a molecular weight of 160 kDa. Dextransucrase activity was inhibited 80–90% by 0.04 mM tannic acid (TA) or 0.4 mM gallic acid (GA) suggesting that tannic acid has 10- fold more inhibitory potential than gallic acid on the activity of dextransucrase. CD/ORD studies revealed modifications in the tertiary structure of enzyme protein in presence of tannic acid and gallic acid, which were further confirmed by fluorescence spectra of the protein in presence of tannic acid. These results suggest that inhibition of dextransucrase activity in S. mutans by polyphenols may have potential applications in the prevention and control of dental caries.     

A facile purification of Leuconostoc mesenteroides B-512FM dextransucrase

Leuconostoc mesenteroides NRRL B-512F has been mutated by treatment with N-nitrosoguanidine. The resulting mutant (designated as B-512FM) produces 300 times as much enzyme as the parent strain. B-512FM dextransucrase was treated extensively with Sigma crude dextranase, followed by column chromatography on Bio-Gel A-5m. The purified dextransucrase had a specific activity of 84 IU/mg, a 100-fold purification with 42% yield, and was shown by SDS-PAGE to have a single protein of molecular weight of 158,000 with dextransucrase activity. The procedure has been used to produce purified enzyme for sequencing. The molecular weight of 158,000 agrees with that calculated from its amino acid sequence.     

Structure modeling and functional analysis of recombinant dextransucrase from Weissella confusa Cab3 expressed in Lactococcus lactis

The dextransucrase gene from Weissella confusa Cab3, having an open reading frame of 4.2?kb coding for 1,402?amino acids, was amplified, cloned, and expressed in Lactococcus lactis. The recombinant dextransucrase, WcCab3-rDSR was expressed as extracellular enzyme in M17 medium with a specific activity of 1.5?U/mg which after purification by PEG-400 fractionation gave 6.1?U/mg resulting in 4-fold purification. WcCab3-rDSR was expressed as soluble and homogeneous protein of molecular mass, approximately, 180?kDa as analyzed by SDS-PAGE. It displayed maximum enzyme activity at 35°C at pH 5.0 in 50?mM sodium acetate buffer. WcCab3-rDSR gave K_m of 6.2?mM and V_m of 6.3?µmol/min/mg. The characterization of dextran synthesized by WcCab3-rDSR by Fourier transform infrared and nuclear magnetic resonance spectroscopic analyses revealed the structural similarities with the dextran produced by the native dextransucrase. The modeled structure of WcCab3-rDSR using the crystal structures of dextransucrase from Lactobacillus reuteri (protein data bank, PDB id: 3HZ3) and Streptococcus mutans (PDB id: 3AIB) as templates depicted the presence of different domains such as A, B, C, IV, and V. The domains A and B are circularly permuted in nature having (β/α)₈ triose phosphate isomerase-barrel fold making the catalytic core of WcCab3-rDSR. The structure superposition and multiple sequence alignment analyses of WcCab3-rDSR with available structures of enzymes from family 70 GH suggested that the amino acid residue Asp510 acts as a nucleophile, Glu548 acts as a catalytic acid/base, whereas Asp621 acts as a transition-state stabilizer and these residues are found to be conserved within the family.     

An analysis of the extracellular xylanases and cellulases of Butyrivibrio fibrisolvens H17c

The extracellular xylanase and cellulase components of Butyrivibrio fibrisolvens H17c were investigated. Two major peaks of enzyme activity were eluted by hydroxylapatite chromatography and designated complex A (CA), having cellulase activity, and complex B (CB) having predominantly xylanase activity but with some activity on carboxymethyl cellulose (CMC). CB was further purified on a DE-52 column and subjected to gel filtration. The xylanase and CMCase activities eluted in a single peak with an apparent molecular mass greater than thyroglobulin (Mr 669,000). CMC xymograms of polyacrylamide gels electrophoresed under non-denaturing conditions indicated the presence of five bands with CMCase activity from CA and eight from CB. Xylan xymograms under the same conditions indicated the presence of four bands of activity in CB. Under mild denaturing conditions the xylanase activity in CB was found in 11 bands with molecular mass ranging from 45 to 180 and the CMCase activity in three bands with molecular mass ranging from 45 kDa to 60 kDa. This indicates that CB exists as a multi-subunit protein aggregate of xylanases, some of which also have cellulase activity.     

Subunit structure of AMP-deaminase from skeletal muscles

AMP-deaminase was purified from skeletal muscle of rat by the affinity chromatography on phosphocellulose and gel-filtration on Sephadex G-200. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS-PAGE) has shown three protein bands on each step of purification. One of them corresponds to the subunit of tetrameric AMP-deaminase molecule with molecular weight of 76 kDa and two others--to the protein subunit with molecular weight of 42 and 33 kDa. Repeated SDS-PAGE of the main subunit band has revealed again all these protein bands. The data obtained indicate that AMP-deaminase subunit of 76 kDa is able to dissociate on two polypeptide chains with similar values of molecular weights in the presence of SDS.     

Leuconostoc mesenteroides B-1355 Mutants Producing Alternansucrases Exhibiting Decreases in Apparent Molecular Mass

Mutants of Leuconostoc mesenteroides B-1355 exhibiting decreases in the apparent molecular mass of alternansucrase on sodium dodecyl sulfate (SDS)-polyacrylamide gels stained for enzyme activity were isolated after mutagenizing strain R15 with N-methyl-N(prm1)-nitro-N-nitrosoguanidine. Strain R15 was a UV mutant of strain B-1355 which was enriched for production of alternansucrase. All strains produced principal and minor alternansucrase bands on SDS gels when cultures were subjected to SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The patterns of the principal and minor activity bands on our SDS gels did not result from dextran-enzyme complexes, because mutants constitutive for synthesis of glucosyltransferases (GTFs) on sugars other than sucrose produced activity bands after growth in glucose medium that were the same as those produced after growth in sucrose medium. Dextransucrase, which had been inactivated by heating at 45(deg)C, was reactivated when subjected to SDS-PAGE, showing that our SDS-PAGE conditions were reversibly denaturing. Thermal denaturation at 45(deg)C did not involve a dispersal of GTFs into subunits. Densitometry measurements showed a roughly linear relationship between enzyme activity and band intensity over a loading range of 0.2 to 0.8 mU per sample well. We concluded that SDS-PAGE followed by activity staining was a reliable method for estimating numbers and ratios of GTFs produced by Leuconostoc sp. in media containing sucrose.     

Enzymatic synthesis of lignin: purification to homogeneity of the three O-methyltransferases of tobacco and production of specific antibodies

Three o-diphenol-O-methyltransferases (OMTs; EC 2.1.1.6) involved in the biosynthesis of lignin have been purified to homogeneity from tobacco leaves. Seven different fractionation steps which included (NH4)2 SO4 precipitation, conventional low-pressure chromatography on Ultrogel AcA34 and DEAE-cellulose columns, high-performance liquid chromatography (HPLC) on three different supports (Mono Q, Mono P, and TSK G-3000 SW columns), and finally preparative electrophoresis were necessary. At each step of purification, the protein content of the enzymatic fractions was analyzed by electrophoresis on polyacrylamide gels under denaturing conditions. Purified OMT I appeared on sodium dodecyl sulfate-polyacrylamide gel as a doublet with electrophoretic mobilities corresponding to molecular weights of 38,500 +/- 2000 and 39,500 +/- 2000. The other two enzymes migrated as single but rather broad bands with molecular weights of 42,000 (OMT II) and 43,000 (OMT III). Polyclonal antibodies were raised in rabbits. The titers of antibodies were measured by an indirect enzyme-linked immunosorbent assay method, and their specificity was demonstrated by immunoblotting enzyme preparations at different stages of purification. Immunodetection of the three enzymes with a specific antiserum suggested serological relationships between the three OMTs of tobacco.     

Guanylate cyclase in Escherichia coli. I. Purification of the enzyme and evidence for an inhibitor]

Guanylate cyclase activity is present in crude E. coli extract. Guanylate cyclase has been purified 3500 fold from this extract, through ammonium sulfate fractionation, DEAE-cellulose chromatography. Sephadex G-75 gel-filtration and polyacrylamide gel preparative microelectrophoresis. During the purification a guanylate cyclase inhibitor has been separated.     

Purification of the prothoracicotropic hormone from the tobacco hornworm Manducasexta

Standard biochemical procedures were used to purify the prothoracicotropic hormone (PTTH) 4400 fold from whole head extracts of $\text{Mandura}$$\text{sexta}$ fifth instar larvae. Hormonal activity was bioassayed by injection into neck-ligated fourth instar larvae. The hormone was stable to heating at 85°C. Ammonium sulfate and acetone fractionation provided a crude preparation which showed dose-dependent activity in the bioassay. Chromatography on Sephadex G-100, DEAE-Sephadex, and hydroxylapatite gave a preparation with 2.6 $\text{Manduca}$ PTTH units/μg protein (4400-fold purification). Activity was sensitive to proteolytic enzymes. Further purification by preparative electrophoresis gave a preparation which migrated as a single band in two polyacrylamide gel electrophoresis systems. A molecular weight estimate of 25,000 Daltons was obtained for this bands on SDS polyacrylamide gels.     

Isolation and purification of a Campylobacter upsaliensis autolysin.

Autolytic activity in the soluble and sediment fractions of sonicates of the spiral and the coccoid form of Campylobacter upsaliensis could not be demonstrated by native (nondenaturing) polyacrylamide gel electrophoresis (PAGE). Autolysins were detected, however, by using denaturing sodium dodecyl sulfate (SDS)-PAGE gels containing either purified Escherichia coli peptidoglycan or whole cells of Micrococcus luteus (Micrococcus lysodeikticus) as the turbid substrate, with subsequent renaturation by treatment with Triton X-100 buffer. In renaturing gels that contained Escherichia coli peptidoglycan, 14 putative autolytic bands ranging from 200 to 12 kDa were detected. In similar gels containing whole cells of M. luteus, only a single band appeared with a molecular mass of 34 kDa. This band corresponded to one of the bands present in the gels containing Escherichia coli peptidoglycan. This common autolysin was isolated by adsorbing it from Campylobacter upsaliensis soluble fractions onto M. luteus cells and then subjecting these cells to renaturing SDS-PAGE in gels containing Escherichia coli peptidoglycan. The 34-kDa autolysin differed from a single 51-kDa autolysin unique to the M. luteus cells, and when isolated from an SDS-PAGE gel, was pure when tested by isoelectric focusing. The N-terminal amino acid sequence analysis showed the first 15 amino acids of the 34-kDa autolysin to have 67% identity to a part of antigenic protein PEB4 of Campylobacter jejuni. The purified autolysin was used to immunize rabbits and the antibodies produced precipitated autolytic activity from cell lysates. The specificity of the antibodies was shown by Western blotting: only a single specific band occurred, with a molecular mass of 34 kDa, and thus it seems unlikely that the 34-kDa autolysin was derived from any of the other autolysins that were detected.     

Immunologically reactive multiple species of mitochondrial coupling factor B

Earlier work had indicated that mitochondrial coupling factor B (FB) could be obtained with differing molecular weights, a highly active 13,000 form, a 29,200 form with low activity, and a partially purified 46,000 form with activity higher than the 29,200 form. We have analyzed FB preparations of different purity and after different types of treatment on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE), followed by silver staining or immunostaining either with rabbit anti-FB serum or monoclonal FB antibody. Highly purified preparations which appear as single bands in SDS-PAGE develop additional higher molecular weight bands (silver staining), including a 48,000 and a 68,000 band, after lyophilization or repeated freezing and thawing or if subjected to SDS-PAGE in the absence of thiol compounds. FB prepared without addition of dithiothreitol and glycerol for stabilization also shows high molecular weight forms, although the active fractions are obtained consistently in the final gel filtration step of purification at a position corresponding to Mr = 13,000. When FB preparations are analyzed by immunoblots of SDS-PAGE using a monoclonal antibody to FB, fresh preparations of purified FB show a single band, while multiple bands are seen in samples which have been frozen and thawed repeatedly. Preparations made in the absence of dithiothreitol and glycerol also show cross-reactive forms of high molecular weight. Similar immunoblots using rabbit antiserum with mitochondria, its extracts, and partially purified FB preparations, all show the presence of several higher molecular weight forms. It is concluded that FB is probably a monomer in mitochondria, and it appears to undergo oligomerization after extraction and during purification.     

Production,purification, and properties of dextransucrase from Leuconostoc mesenteroides NRRL B-512F

The production of dextransucrase fromLeuconostoc mesenteroides NRRL B-512F was stimulated 2-fold by the addition of 0.005% of calcium chloride to the medium; levansucrase levels were unaffected. Dextransucrase was purified by concentration and dialysis of the culture supernatant with a Bio-Fiber 80 miniplant, and by treatment with dextranase followed by chromatography on Bio-Gel A-5m. A 240-fold purification, with a specific activity of 53 U/mg, was obtained. Contaminating enzyme activities of levansucrase, invertase, dextranase, glucosidase, and sucrose phosphorylase were decreased to non-detectable levels. Poly(acrylamide)-gel electrophoresis of the purified enzyme showed only two protein bands, both of which had dextransucrase activity. These bands also gave a carbohydrate stain, indicating that the dextransucrase could be a glycoprotein. Acid hydrolysis, followed by paper chromatography, of the purified enzyme showed that the major carbohydrate was mannose. ConcanavaIin A completely removed dextransucrase activity from solution, confirming the mannoglycoprotein character of the enzyme. Dextransucrase activity was not altered by the addition of 0.008?4 mg/ml of dextran, but its storage stability was increased by the addition of 4 mg/ml of dextran. As previously shown by others, the activity of dextransucrase was decreased by EDTA, and was restored by the addition of calcium ions. Zinc, cadmium, lead, mercury, and copper ions were inhibitory to various degrees.     

Resolution of two subunits from the molybdenum-iron protein of Azotobacter vinelandii nitrogenase

The Mo-Fe protein of Azotobacter vinelandii nitrogenase was fractionated on 9.5 M urea isoelectric focusing gels and gave three distinct bands (alpha', alpha", beta'). Protein focused on nondenaturing gels gave a single brown band, which when excised and refocused on a denaturing gel gave the three-band pattern. Partial trypsin digestion of the subunits and fractionation of the peptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the alpha' and alpha" polypeptide moieties were the same. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the alpha' and beta' proteins with appropriate molecular weight standards indicated Mr = 61,000 and 57,000, respectively. This is consistent with an overall alpha 2 beta 2 mass of 236,000 daltons.     

Purification and partial characterization of marinocine, a new broad-spectrum antibacterial protein produced by Marinomonas mediterranea

This work describes the purification and partial characterization of a novel antibacterial compound, here named marinocine, produced by Marinomonas mediterranea, a melanogenic marine bacterium with rich secondary metabolism. The antibacterial compound is a protein detected in the medium at death phase of growth. It has been purified to apparent homogeneity from the supernatants of cultures by means of ethanol precipitation followed by column chromatographies on DEAE-Sephadex and Sephacryl HR-200. The protein has an apparent molecular mass of 140-170 kDa according to gel permeation chromatography and non-denaturing SDS-PAGE, although in denaturing SDS-PAGE two mayor bands of 97 and 185 kDa appear. Marinocine is relatively heat-stable and shows a great resistance against many hydrolytic enzymes such as glycosidases, lipase, and proteases. The antibacterial range of the molecule includes Gram-positive and Gram-negative microorganisms, as well as some nosocomial isolates, Staphylococcus aureus and Pseudomonas sp., highly resistant to classical antibiotics. By contrast, marinocine did not show any effect on the eukaryotic microorganisms tested. Regarding eukaryotic CHO cells, the decrease on viability was much lower than the one observed on bacterial cells.     

Isolation and glucose-6-phosphate-mediated dimerization of hexokinase from human heart

Soluble hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) was purified from human heart. 1 kg of tissue provided 25 mg hexokinase with a specific activity of 58 units/mg, representing a 1700-fold purification and 47% yield. The purification involved six steps, including affinity chromatography with glucosamine attached to Sepharose. The material was homogeneous according to electrophoresis, gel-filtration and sedimentation in the ultracentrifuge, but gave two main components on electrophoresis in denaturing conditions. From determination of the sedimentation and diffusion coefficients, the relative molecular mass was calculated to be 105 000. The enzyme is monomeric, but glucose 6-phosphate promotes an association to dimers. This effect is reversible and is independent of the concentrations of glucose or inorganic phosphate. The results support the postulate that soluble and mitochondrion-bound hexokinases are identical.     

Purification of bovine cathepsin B: proteomic characterization of the different forms and production of specific antibodies.

Cathepsin B (EC 3.4.22.1) has been highly purified (14,225 fold) from bovine kidney by a rapid procedure that included the preparation of an enriched lysosomal extract, a selective fractionation with ammonium sulphate, size-exclusion chromatography, two cation-exchange chromatographies, and anion-exchange chromatography on diethylaminoethyl-Sephacel. After the last purification step, two hydrolytic peaks against Z-Phe-Arg-AMC were separated from each other, a minor peak corresponding to the cathepsin B single-chain form and a major one representing the double-chain form of cathepsin B. The single-chain form showed a molecular mass of 31 kDa on sodium dodecyl sulphate - polyacrylamide gel electrphoresis (PAGE) under reducing conditions, whereas the heavy chain of the double-chain form appeared as a doublet with molecular masses of 23.4 and 25 kDa, respectively. The identity of the different cathepsin B isoforms and the quality of the final enzyme preparation were confirmed by using two types of antibodies, one against a synthetic peptide sequence and one against purified cathepsin B. The proteomic study confirmed the identity of the different SDS-PAGE protein bands as cathepsin B isoforms and allowed the comparison and study of some structural differences between them at the level of their primary structures.     

The purification and polypeptide composition of avian infectious bronchitis virus.

Purification of egg-grown infectious bronchitis virus (IBV) by sucrose density gradient centrifugation alone, or sucrose density gradient centrifugation plus pH 8.0 treatment, concanavalin A precipitation or metrizamide density gradient centrifugation, failed to produce any differences in the virus polypeptide pattern following polyacrylamide gel electrophoresis in the presence of SDS(SDS-PAGE). SDS-PAGE of purified IBV on 7.5% acrylamide gels separated 16 polypeptides which were detectable by staining with Coomassie blue or measurement of radioactivity following electrophoresis of (3H)-leucine labelled IBV. The molecular weights of the polypeptides were within the range 15,000-135,000. The polypeptides of egg and chick kidney (CK) cell-grown IBV were identical in both size and number but quantitative differences were detected. In particular the relative proportion of the major 52,000 molecular weight polypeptide was greatly reduced in IBV grown in CK cells. SDS-PAGE of purified IBV and staining with Schiff's reagent to detect carbohydrate revealed four.bands with molecular weights of 128,000, 86,000, 67,500 and 37,000. The 128,000 band did not correspond to any of the detected polypeptides. Use of 5% acrylamide gels for SDS-PAGE of IBV failed to resolve all the minor polypeptides and only seven bands were detected.     

Experimental allergic orchitis: the isolation and partial characterization of an aspermatogenic polypeptide (AP3) with an apparent sequential disease-inducing determinant(s)

An aspermatogenic polypeptide (AP3) capable of inducing experimental allergic orchitis (EAO) in the guinea pig (GP) was purified from GP testes by sequential delipidation, acid extraction, pH precipitation, ammonium sulfate fractionation, trichloroacetic acid precipitation, gel filtration on Sephadex G-75, preparative isoelectric focusing from pH 3-10 followed by isoelectric focusing from pH 7-10, gel filtration on Sephadex G-75 Superfine under reducing conditions, and reduced acid urea gel electrophoresis. Approximately 250 micrograms (BSA equivalents) of AP3 were obtained from 500 g wet weight of GP testes. On 15% reduced acid urea polyacrylamide gels, AP3 appeared as a single band with an Rf of 0.19. SDS-PAGE showed a single band with a mobility corresponding to a m.w. of 12,500 +/- 1500. The isoelectric point, determined during purification, was 9.90 +/- 0.50. Amino acid analysis of AP3 indicates it is a protein. Gas liquid chromatographic analysis failed to reveal the presence of either hexose or hexosamine, indicating that AP3 is probably not a glycopeptide. Two to 5.0 micrograms (BSA equivalents) of AP3 are capable of inducing severe EAO in 100% of GP tested; 1 to 2.0 micrograms (BSA equivalents) induced EAO in 60% of GP tested. Because AP3 appears to be nonglycosylated and the aspermatogenic activity of AP3 is highly resistant to various denaturing conditions including reduction and alkylation, the primary sequence of the polypeptide rather than higher ordered structure may be more important in defining the determinant(s) responsible for its aspermatogenic activity.     

Purification of aspartate transcarbamoylase from Pseudomonas syringae

Abstract The aspartate transcarbamoylase (ATCase) from Pseudomonas syringae has been purified. The purified enzyme was shown by SDS-PAGE to give two bands. Unambiguous results from N-terminal sequencing suggested that each band represented a homogeneous polypeptide. The M _r (relative molecular mass) of the polypeptides was estimated to be 47 kDa and 34 kDa. The M _r of the holoenzyme determined by gel filtration and electrophoretic migration in polyacrylamide gradient gels under non-denaturing conditions was estimated at approximately 490 kDa. These findings suggest a subunit structure different from any previously described for a bacterial ATCase.