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Isolation and characterization of DNA-dependent RNA polymerase III from Leishmania mexicana and inhibition by purine analogs.

Nolan, L L; Fehr, T F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1987 EN
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A DNA-dependent RNA polymerase has been isolated and characterized from the parasitic flagellated protozoan Leishmania mexicana. The initial stages of purification utilized high-ionic-strength extraction and protamine sulfate treatment. The enzyme was further purified by differential elution by heparin-Sepharose, DEAE-Sephadex, and carboxymethyl-Sephadex chromatography. Analysis of the chromatographically purified RNA polymerase on nondenaturing gels revealed two electrophoretic forms. The enzyme isolated had characteristics of true DNA-dependent RNA polymerase since it required DNA and all four nucleoside triphosphates for synthesis of RNase-sensitive products. Analysis of ammonium sulfate and metal ion optima, as well as relative activities of the enzyme with Mn2+ versus Mg2+, gave results similar to those reported for other RNA polymerase IIIs in eucaryotes. Formycin A triphosphate was found to be a noncompetitive inhibitor of RNA polymerase III, and cordycepin triphosphate was found to be inhibitory, although the exact mode of inhibition was not determined.

Multiple glucan-binding proteins of Streptococcus sobrinus.

Ma, Y; Lassiter, M O; Banas, J A; Galperín, M Y; Taylor, K G; Doyle, R J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1996 EN
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Several proteins from culture supernatants of Streptococcus sobrinus were able to bind avidly to Sephadex G-75. The proteins could be partially eluted from the Sephadex by low-molecular-weight alpha-1,6 glucan or fully eluted by 4 M guanidine hydrochloride. Elution profiles were complex, yielding proteins of 16, 45, 58 to 60, 90, 135, and 145 kDa, showing that the wild-type strain possessed multiple glucan-binding proteins. Two mutants of Streptococcus sobrinus incapable of aggregation by high-molecular-weight alpha-1,6 glucan were isolated. One mutant was spontaneous, from a cell suspension to which glucan had been added, whereas the other was induced by ethyl methanesulfonate. Both mutants were devoid of a 60-kDa protein, as shown by gel electrophoresis of culture supernatants and whole cells. Amino acid analysis showed that the 58- to 60-kDa protein and the 90-kDa protein were distinct, although both were N-terminally blocked. Both mutants retained their ability to adhere to glass in the presence of sucrose and to ferment mannitol and sorbitol. Both mutants retained their glucosytransferase activities, as shown by activity gels. Western blots (immunoblots), employing antibody against a glucan-binding protein of Streptococcus mutans...

Purification and characterization of a new xylanase (APX-II) from the fungus Aureobasidium pullulans Y-2311-1.

Li, X L; Zhang, Z Q; Dean, J F; Eriksson, K E; Ljungdahl, L G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1993 EN
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Aureobasidium pullulans Y-2311-1 produced four major xylanases (EC 3.2.1.8) with pI values of 4.0, 7.3, 7.9, and 9.4 as revealed by isoelectric focusing and zymogram analysis when grown for 4 days on 1.0% oat spelt xylan. The enzyme with a pI of 9.4 was purified by ammonium sulfate precipitation, chromatography on a DEAE-Sephadex A-50 column, and gel filtration with a Sephadex G-75 column. The enzyme had a mass of about 25 kDa as determined by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography. The purified enzyme had a Km of 7.6 mg . ml(-1) and Vmax of 2,650 micromol . min(-1) . mg(-1) for birchwood xylan at 28 degrees C and pH 4.5. It lacked activity towards carboxymethylcellulose, cellobiose, starch, mannan, p-nitrophenyl (pNP)-beta-D-xylopyranoside, pNP-beta-D-glucopyranoside, pNP-alpha-D-glucopyranoside, pNP-beta-D-cellobioside, pNP-beta-D-fucopyranoside, or pNP-alpha-D-galactopyranoside. The predominant end products of birchwood xylan or xylohexaose hydrolysis were xylobiose and xylose. The enzyme had the highest activity of pH 4.8 and 54 degrees C. Sixty percent of the activity remained after the enzyme had been incubated at 55 degrees C and pH 4.5 for 30 min. The sequence of the first 68 amino acid residues at the amino terminus showed homology to those of several other xylonases. Immunoblot analysis with antiserum raised against the purified xylanase revealed that two immunologically related polypeptides of 25 and 22 kDa were produced in A. pullulans cultures containing oat spelt xylan or xylose as carbon sources but not in cultures containing glycerol or glucose.

Purification and Characterization of a Keratinase from a Feather-Degrading Bacillus licheniformis Strain

Lin, Xiang; Lee, Chung-Ginn; Casale, Ellen S.; Shih, Jason C. H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1992 EN
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A keratinase was isolated from the culture medium of feather-degrading Bacillus licheniformis PWD-1 by use of an assay of the hydrolysis of azokeratin. Membrane ultrafiltration and carboxymethyl cellulose ion-exchange and Sephadex G-75 gel chromatographies were used to purify the enzyme. The specific activity of the purified keratinase relative to that in the original medium was approximately 70-fold. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and Sephadex G-75 chromatography indicated that the purified keratinase is monomeric and has a molecular mass of 33 kDa. The optimum pH and the pI were determined to be 7.5 and 7.25, respectively. Under standard assay conditions, the apparent temperature optimum was 50°C. The enzyme is stable when stored at −20°C. The purified keratinase hydrolyzes a broad range of substrates and displays higher proteolytic activity than most proteases. In practical applications, keratinase is a useful enzyme for promoting the hydrolysis of feather keratin and improving the digestibility of feather meal.

Purification and Properties of Clostridium botulinum Type F Toxin

Yang, K. H.; Sugiyama, H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1975 EN
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Clostridium botulinum type F toxin of proteolytic Langeland strain was purified. Toxin in whole cultures was precipitated with (NH4)2SO4. Extract of the precipitate was successively chromatographed on diethylaminoethyl-cellulose at pH 6.0, O-(carboxymethyl) cellulose at pH 4.9, Sephadex G-200 at pH 8.1, quaternary aminoethyl-Sephadex at pH 4.9, and finally diethylaminoethyl-cellulose at pH 8.1. The procedure recovered 14% of the toxin assayed in the starting culture. The toxin was homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, double gel diffusion serology, and isoelectric focusing. Purified toxin had a molecular weight of 150,000 by gel filtration and 155,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Specific toxicity was 9.6 × 106 mean lethal doses per absorbancy (278 nm) unit. Sub-units of 105,000 and 56,000 molecular weight are found when purified toxin is treated with a disulfide reducing agent and electrophoresed on sodium dodecyl sulfate-polyacrylamide gels. Reciprocal cross neutralizations were demonstrated when purified type F and E toxins were reacted with antitoxins which were obtained with immunizing toxoids prepared with purified toxins.

Rapid method for separation of bacterial DNA from humic substances in sediments for polymerase chain reaction.

Tsai, Y L; Olson, B H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1992 EN
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The polymerase chain reaction (PCR) was used to amplify an Escherichia coli 16S ribosomal gene fragment from sediments with high contents of humic substances. Total DNA was extracted from 1 g of E. coli seeded or unseeded samples by a rapid freeze-and-thaw method. Several approaches (use of Bio-Gel P-6 and P-30 and Sephadex G-50 and G-200 columns, as well as use of the Stoffel fragment) were used to reduce interference with the PCR. The best results were obtained when crude DNA extracts containing humic substances were purified by using Sephadex G-200 spun columns saturated with Tris-EDTA buffer (pH 8.0). Eluted fractions were collected for PCR analyses. The amplified DNA fragment was obtained from seeded sediments containing fewer than 70 E. coli cells per g. Because only 1/100 of the eluted fractions containing DNA extracts from 70 cells per g was used for the PCR, the sensitivity of detection was determined to be less than 1 E. coli cell. Thus, DNA direct extraction coupled with this technique to remove interference by humic substances and followed by the PCR can be a powerful tool to detect low numbers of bacterial cells in environmental samples containing humic substances.

Localization and Characterization of α-Glucosidase Activity in Lactobacillus brevis

De Cort, S.; Kumara, H. M. C. Shantha; Verachtert, H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1994 EN
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Lactobacillus brevis is found together with the yeast Brettanomyces lambicus during the overattenuation process in spontaneously fermented lambic beer. An isolated L. brevis strain has been shown to produce an α-glucosidase with many similarities to the glucosidase earlier found in B. lambicus. The enzyme was purified by ammonium sulfate precipitation, gel (Sephadex G-150 and Ultrogel AcA-44) filtration, and ion-exchange chromatography (DEAE-Sephadex A-50). The molecular weights of the enzyme, as determined by gel chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were about 50,000 and 60,000, respectively. Optimum catalytic activity was obtained at 40°C and pH 6.0. The enzyme showed a decrease of hydrolysis with an increase in the degree of polymerization of the substrate. The Km values for p-nitrophenyl-α-d-glucopyranoside, maltose, and maltotriose were 0.51, 3.0, and 5.2 mM, respectively. There was lack of inhibition by 0.15 mM acarbose and 0.5 M turanose, but the enzyme was inhibited by Tris (Ki value of 25 mM). The α-glucosidase of L. brevis together with the enzyme of B. lambicus seems to be a key factor in the overattenuation of lambic beer, although the involvement of other lactic acid bacteria (pediococci) cannot be excluded.

Requirement of heat-labile cytoplasmic protein factors for posttranslational translocation of OmpA protein precursors into Escherichia coli membrane vesicles.

Weng, Q P; Chen, L L; Tai, P C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1988 EN
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The involvement of possible cytoplasmic factors in ATP-dependent postttranslational translocation of proteins into Escherichia coli membrane vesicles was examined. The precursor of OmpA protein was partially purified by DEAE-cellulose chromatography, and its translocation was found to require material from the soluble cytoplasmic fraction. The fractionated active cytoplasmic translocation factor (CTF) was protease sensitive, micrococcal nuclease insensitive, N-ethylmaleimide resistant, and heat labile. The heat sensitivity of the CTF allowed its specific and preferential inactivation in the crude-precursor synthesis mixture, which provided a simple and rapid assay procedure for the factor during purification. Two active fractions were detected upon further fractionation: the major one was about 8S in sucrose gradient centrifugation and 120 kilodaltons by Sephadex filtration, whereas the other was about 4S and 60 kilodaltons in sucrose gradient centrifugation and by Sephadex filtration, respectively. The active fractions could also be fractionated by DEAE-Sepharose chromatography. These CTFs are apparently different from the previously reported 12S export factor (M. Muller and G. Blobel, Proc. Natl. Acad. Sci. USA 81:7737-7741, 1984).

Partial purification and some properties of homoserine O-acetyltransferase of a methionine auxotroph of Saccharomyces cerevisiae.

Yamagata, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1987 EN
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A wild-type strain and six methionine auxotrophs of Saccharomyces cerevisiae were cultured in a synthetic medium supplemented with 0.1 mM L-cysteine or L-methionine and analyzed for the synthesis of homoserine O-acetyltransferase (EC 2.3.1.31). Among them, four mutant strains exhibited enzyme activity in cell extracts. Methionine added to the synthetic medium at concentrations higher than 0.1 mM repressed enzyme synthesis in two of these strains. The enzyme was partially purified (3,500-fold) from an extract of a mutant strain through ammonium sulfate fractionation and chromatography on columns of DEAE-cellulose, Phenyl-Sepharose C1-4B, and Sephadex G-150. The enzyme exhibited optimal pH at 7.5 for activity and at 7.8 for stability. The reaction product was ascertained to be O-acetyl-L-homoserine by confirming that it produced L-homocysteine in an O-acetyl-L-homoserine sulfhydrylase reaction. The Km for L-homoserine was 1.0 mM, and for acetyl coenzyme A it was 0.027 mM. The molecular weight of the enzyme was estimated to be approximately 104,000 by Sephadex G-150 column chromatography and 101,000 by sucrose density gradient centrifugation. The isoelectric point was at pH 4.0. Of the hydroxy amino acids examined, the enzyme showed reactivity only to L-homoserine. Succinyl coenzyme A was not an acyl donor. In the absence of L-homoserine...

Oxidation of aromatic alcohols by purified methanol dehydrogenase from Methylosinus trichosporium.

Mountfort, D O
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1990 EN
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Methanol dehydrogenase was found to be present in subcellular preparations of methanol-grown Methylosinus trichosporium and occurred almost wholly in the soluble fraction of the cell. The enzyme, purified by DEAE-Sephadex and Sephadex G-100 chromatography, showed broad specificity toward different substrates and oxidized the aromatic alcohols benzyl, vanillyl, and veratryl alcohols in addition to a range of aliphatic primary alcohols. No enzyme activity was found toward the corresponding aldehydes of the alcohols tested. The Km for methanol was 50 microM, and that for the aromatic alcohols was in the range of 1 to 2 mM. EDTA and p-nitrophenylhydrazine, which are inhibitors of methanol oxidation in whole cells of methylotrophs, had little effect on activity of the purified enzyme. The results now extend the range of substrates oxidized by methanol dehydrogenase to include the aromatic alcohols.

Uracil phosphoribosyltransferase from Acholeplasma laidlawii: partial purification and kinetic properties.

McIvor, R S; Wohlhueter, R M; Plagemann, P G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1983 EN
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Uracil phosphoribosyltransferase was purified 34-fold from sonicated extracts of Acholeplasma laidlawii by ammonium sulfate precipitation, binding to DEAE-Sephadex, Sephadex G-200 chromatography, and hydroxylapatite chromatography. The molecular weight of the enzyme by gel filtration was approximately 80,000. The pH optimum for phosphoribosylation was around 7.5, and the optimum MgCl2 concentration was 5 mM. Initial velocity studies were conducted over a wide range of both uracil and 5-phosphoribosyl-1-pyrophosphate (P-Rib-PP) concentrations, and various equations for biomolecular reaction mechanisms were fitted to the data by nonlinear regression. When the equation for an ordered sequential mechanism was fitted to the data, the Kia thus obtained was not statistically different from zero. This is interpreted as evidence for a nonsequential ("ping-pong") reaction. Graphic analysis of the data by the Hanes-Woolf linear transform supported this conclusion. The enzyme has high affinity for uracil (KmUra = 4.2 microM; KmP-Rib-PP = 66 microM), which provides supporting evidence that this activity is responsible for the incorporation of uracil and uridine into nucleotides.

Uridine phosphorylase from Acholeplasma laidlawii: purification and kinetic properties.

McIvor, R S; Wohlhueter, R M; Plagemann, P G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1983 EN
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Uridine phosphorylase was purified 1,370-fold from sonicated extracts of Acholeplasma laidlawii by ammonium sulfate precipitation, DEAE-Sephadex column chromatography, hydroxylapatite chromatography, and Sephadex G-200 fractionation. The molecular weight of the enzyme as determined by gel filtration was approximately 65,000. [U-14C]ribose-1-phosphate (Rib-1-P), prepared enzymatically from [U-14C]inosine, was utilized in initial velocity studies of uridine synthesis, which indicated a sequential reaction with a KmUra of 110 microM and a KmRib-1-P of 17 microM. The kinetics of uridine cleavage were assessed at a saturating cosubstrate concentration, resulting in a KmUrd of 170 microM and a KmPi of 120 microM. These results indicate that an intracellular flux from uracil to uridine is kinetically feasible. However, such flux would be metabolically unproductive, since the low affinity of uridine kinase (KmUrd = 3.2 mM) precludes the operation of uridine phosphorylase and uridine kinase in tandem to convert uracil to UMP. We conclude that uridine phosphorylase performs only a catabolic function in A. laidlawii.

Purification of a soluble and a wall-bound form of beta-glucosidase from Mucor racemosus.

Borgia, P I; Mehnert, D W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1982 EN
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beta-Glucosidase activity in crude extracts of Mucor racemosus exists in a soluble form and in a wall-bound form which sediments at 3,500 x g. The soluble form and a wall-bound form were purified to homogeneity by ammonium sulfate fractionation. DEAE-Sephadex chromatography, and SP-Sephadex chromatography. Both forms were identical in all parameters measured. Each enzyme is a glycoprotein of 91,000 daltons, with an identical amino acid composition and N-terminal amino acid of lysine; both contain about 10% carbohydrate. Both forms catalyze the hydrolysis of cellobiose and p-nitrophenyl-beta-D-glucoside with identical kinetic constants.

Purification and characterization of the tween-hydrolyzing esterase of Mycobacterium smegmatis.

Tomioka, H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1983 EN
Relevância na Pesquisa
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An esterase hydrolyzing Tween 80 (polyoxyethylene sorbitan monooleate) was purified from sonicated cell lysates of Mycobacterium smegmatis ATCC 14468 by DEAE-cellulose, Sephadex G-150, phenyl Sepharose, and diethyl-(2-hydroxypropyl) aminoethyl column chromatography and by subsequent preparative polyacrylamide gel electrophoresis. The molecular weight was estimated to be 36,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 41,000 by gel filtration on a Sephadex G-150 column. The esterase contained a single polypeptide. The esterase was stable to heat treatment at 100 degrees C and to a wide range of pH. The temperature and pH optima for the hydrolysis of Tween 80 were 50 degrees C and 8.3, respectively. The esterase had a narrow substrate specificity; it exhibited a high activity only on compounds having both polyoxyethylene and fatty acyl moieties, such as Tweens. Monoacylglyceride was hydrolyzed more slowly by this esterase and this enzyme exhibited a nonspecific esterase activity on p-nitrophenyl acyl esters, especially those having short chain acyl moieties. The Km and Vmax were 19.2 mM and 1,670 mumol/min per mg of protein for Tween 20, 6.6 mM and 278 mumol/min per mg of protein for Tween 80, and 0.25 mM and 196 mumol/min per mg of protein for p-nitrophenyl acetate...

Extraction and properties of hemagglutinin from cell wall fragments of Fusobacterium nucleatum.

Dehazya, P; Coles, R S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1982 EN
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To study the hemagglutinin of Fusobacterium nucleatum, methods were sought to solubilize and purify this component. When cells of F. nucleatum were ruptured by passage through a French press, the fragments lost virtually all ability to agglutinate human erythrocytes. Extraction of the fragments with 2% Triton X-100 for 30 min at 22 degrees C restored hemagglutinating activity (HA). Hemagglutination by these fragments could be inhibited by arginine, as can hemagglutination by intact bacteria. Treatment of active cell wall fragments with pronase and 2% Triton X-100-EDTA at 37 degrees C or with pronase and 0.1% Triton X-100-EDTA at pH 10.0 allowed recovery of solubilized HA. The former HA was inhibited by arginine (arg+) whereas the latter was not (arg-). Fractionation of the arg+ extract by preparative isoelectric focusing showed that HA was recovered from the gel sections having a pH between 4.5 and 5.5. Hemagglutination by this preparation was still arg+. Chromatography of this hemagglutinin on DEAE-Sephadex increased the specific activity to high levels with a loss of inhibition by arginine. A fraction from the DEAE-Sephadex column containing 10,700 HA units per mg of protein was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Solubilization at 22 degrees C before electrophoresis revealed three Coomassie blue-staining bands which migrated with apparent molecular weights of about 21...

Structure-Function Relationships in the Arginine Pathway Carbamoylphosphate Synthase of Saccharomyces cerevisiae

Piérard, André; Schröter, Brigitte
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1978 EN
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The arginine pathway carbamoylphosphate synthase (CPSase A) from Saccharomyces cerevisiae was shown to be highly unstable and could not be substantially purified. In spite of this instability, a number of important properties of this enzyme were determined with crude preparations. A molecular weight of 140,000 (7.9S) was estimated for the native enzyme by sucrose gradient centrifugation; a significantly higher value, 175,000, was obtained by gel filtration on Sephadex. The enzyme is an aggregate consisting of two protein components, coded for by the unlinked genes cpaI and cpaII. These components were separated by diethylaminoethyl-cellulose chromatography. Their molecular weights, estimated by Sephadex gel filtration, were 36,000 and 130,000. The large component catalyzed the synthesis of carbamoylphosphate from ammonia. The small component was required in addition to the large one for the physiologically functional glutamine-dependent activity. Apparent Michaelis constants at pH 7.5 of 1.25 mM for glutamine and 75 mM for NH4Cl were measured with the native enzyme. The use of various glutamine analogs, including 2-amino-4-oxo-5-chloropentanoic acid, indicated that binding of glutamine to a site located on the small component was followed by transfer of its amide nitrogen to the ammonia site on the heavy component. This ammonia site was able to function independently of the utilization of glutamine. However...

Mycoplasma growth factors in bovine serum fraction.

Washburn, L R; Hughes, J H; Somerson, N L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1978 EN
Relevância na Pesquisa
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Mycoplasma growth factors in bovine serum fraction were separated by Sephadex G150 column chromatography and density ultracentrifugation. The major growth factor of bovine serum fraction eluted from the Sephadex column in the void volume. Its growth-supporting activity was greatly enhanced by the presence of bovine serum albumin in the mycoplasma culture media. Other investigators had previously identified the major growth factor in serum as an alpha-lipoprotein. Although density ultracentrifugation revealed the presence of traces of a high-density lipoprotein in bovine serum fraction, another, less dense component, isolated by ultracentrifugation (component 3) and containing cholesterol, cholesteryl esters, free fatty acids, triglycerides, and protein, but no lipoprotein, exhibited considerably more growth-supporting activity than did the high-density lipoprotein, thus indicating that at least two mycoplasma species do not require intact serum lipoprotein for growth. Both the high-density lipoprotein and component 3 exhibited maximum activity only in the presence of bovine serum albumin. A chloroform extract containing component 3 lipids combined with bovine serum albumin to form an effective, partially defined, less complex substitute for serum in mycoplasma culture media.

PURIFICATION OF MITOGENIC PROTEINS DERIVED FROM Phaseolus vulgaris: ISOLATION OF POTENT AND WEAK PHYTOHEMAGGLUTININS POSSESSING MITOGENIC ACTIVITY

Allen, Lawrence W.; Svenson, Robert H.; Yachnin, Stanley
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1969 EN
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Commercially obtained phytohemagglutinin (PHAP) derived from Phaseolus vulgaris contains 17 different protein bands when analyzed by acrylamide gel electrophoresis. When it is subjected to CM-Sephadex chromatography followed by molecular sieving on Sephadex G150, several species of potent mitogenic proteins, which differ greatly in their hemagglutinating capacity, are obtained. A low hemagglutinating mitogen (L-PHAP), homogeneous by several different criteria, is the most potent mitogen isolated, and also possesses potent leukoagglutinating activity. It is a glycoprotein with a molecular weight of 115,000, containing glucosamine, mannose, xylose, and fucose or arabinose. Also isolated is a mixture of at least two closely related proteins possessing high hemagglutinating capacity, with hemagglutination titers 250 times more potent than L-PHAP. This material is a slightly less potent mitogen than L-PHAP and also possesses leukoagglutinating capacity, although of a lower order of magnitude. Its amino acid and carbohydrate composition are similar to L-PHAP, but it contains approximately twice as much carbohydrate and is slightly larger as determined by molecular sieving.

Purification and properties of a second enzyme catalyzing the splitting of carbon-mercury linkages from mercury-resistant Pseudomonas K-62.

Tezuka, T; Tonomura, K
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1978 EN
Relevância na Pesquisa
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An enzyme (splitting enzyme 2) which catalyzes the splitting of carbon-mercury linkage of arylmercury compounds was found in extracts of mercury-resistant Pseudomonas K-62. This enzyme was purified about 725-fold by treatment with streptomycin, precipitation with ammonium sulfate, and successive chromatography on Sephadex G-75 and diethylaminoethyl-cellulose. A purified preparation of the enzyme showed a single band in electrophoresis either on polyacrylamide or sodium dodecyl sulfate-containing polyacrylamide gels. The molecular weight of the enzyme was estimated to be 20,000 (determined by Sephadex G-75 gel filtration) 17,000 (determined by sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis). The enzyme showed a Km of 180 micron and a Vmax of 3.1 mumol/min per mg for p-chloromercuribenzoic acid and a Km of 250 micron and a Vmax of 20 mumol/min per mg for phenylmercuric acetate. The optimum temperature and pH for the reaction were 40 degrees C and 5.0, respectively.

Purification and some properties of an extracellular alpha-amylase from Bacteroides amylophilus.

McWethy, S J; Hartman, P A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1977 EN
Relevância na Pesquisa
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A medium was developed to obtain maximum yields of extracellular amylase from Bacteroides amylophilus 70. Crude enzyme preparation, obtained by ammonium sulfate precipitation of cell-free broth, contained six amylolytic isoenzymes that were detected by isoelectric focusing and polyacrylamide gel electrophoresis. One of these amylases was purified by diethylaminoethyl-Sephadex A-50 ion-exchange chromatography and Sephadex G-200 gel filtration techniques. Some properties of the purified extracellular alpha-amylase were: optimum pH, 6.3; optimum temperature, 43 degrees C: PH stability range, 5.8 to 7.5; isoelectric point, pH 4.6; molecular weight, 92,000 (by sodium dodecyl sulfatedisc gel electrophoresis); and sugars causing inhibition, cyclomaltoheptaose, cyclomaltohexaose, and alpha-d-phenylglucoside. In addition, Ca2+ and Co2+ were strong activators,and Hg2+ was a strong inhibitior; all other cations were slightly stimulatory. Dialysis against 0.01 M ethylenediaminetetraacetic acid caused a 58% loss of activity that was restored to 92% of the original by the addition of 0.04 M Ca2+. The enzyme affected a blue-value-reducing-value curve characteristic of alpha-type amylases. The relative rates of hydrolysis of amylose, soluble starch...