Purification of β-acetylglucosaminase and β-galactosidase from ram testis

1. The presence of beta-galactosidase (EC 3.2.1.23) in an acetic acid extract of ram testis is reported. Some properties of the crude enzyme preparation were studied. 2. The purification of beta-acetylglucosaminase (EC 3.2.1.30) and of beta-galactosidase from the ram-testis extract by ammonium sulphate precipitation and chromatography on a CM-cellulose column is described. 3. The final purifications of the separated enzymes achieved were for the beta-acetylglucosaminase 35 times and for the beta-galactosidase 99 times. 4. The possibility of using DEAE-cellulose and Sephadex G-200 to purify the enzymes was investigated.     

Cloning and bacterial expression of the CYS3 gene encoding cystathionine gamma-lyase of Saccharomyces cerevisiae and the physicochemical and enzymatic properties of the protein.

By screening a yeast genomic library, we isolated and characterized a gene rescuing the cysteine requirement in a "cys1" strain of Saccharomyces cerevisiae. Except for four residues in the open reading frame composed of 1,182 nucleotides, the DNA sequence was the same as that for the CYS3 (CYI1) gene, encoding cystathionine gamma-lyase (EC 4.4.1.1), and isolated previously as a cycloheximide-induced gene (B. Ono, K. Tanaka, K. Naito, C. Heike, S. Shinoda, S. Yamamoto, S. Ohmori, T. Oshima, and A. Toh-e, J. Bacteriol. 174:pp.3339-3347, 1992). S. cerevisiae "cys1" strains carry two closely linked mutations; one (cys1) causes a defect in serine O-acetyltransferase (EC 2.3.1.30), and another, designated cys3, impairs cystathionine gamma-lyase activity. Rescue of the cysteine requirement by the gene encoding cystathionine gamma-lyase is consistent with both defects being responsible for the cysteine auxotrophy. In an effort to further determine the physicochemical and enzymatic properties of this enzyme, a coding fragment was cloned into an Escherichia coli expression plasmid, and the protein was produced in the bacteria. The induced protein was extracted by sonication and purified to homogeneity through one course of DEAE-cellulose column chromatography. The yield of the protein was approximately 150 mg from cells cultured in 1 liter of L broth. The protein showed molecular weights of approximately 194,000 and 48,000 (for the subunit), suggesting a tetrameric structure. An s20,w value of 8.8 was estimated by centrifugation in a sucrose concentration gradient. No sulfhydryl groups were detected, which is consistent with the absence of cysteine residues in the coding sequence. The isoelectric point was at pH 5.2. The protein showed a number of cystathionine-related activities, i.e., cystathionine beta-lyase (EC 4.4.1.8), cystathionine gamma-lyase, and cystathionine gamma-synthase (EC 4.2.99.9) with L-homoserine as substrate. In addition, we demonstrated L-homoserine sulfhydrylase (adding H2S) activity but could find no detectable serine O-acteyltransferease activity. In this paper, we compare the enzymatic properties of the protein with those of homologous enzymes previously reported and discuss the possibility that this enzyme has a physiological role as cystathionine Beta-lyase and cystathionine gamma-synthase in addition to its previously described role as cystathionine gamma-lyase.     

Human placental sialidase: partial purification and characterization

A sialidase [EC 3.2.1.18] has been partially purified from human placenta by means of procedures comprising Con A-Sepharose adsorption, ammonium sulfate precipitation, sucrose density gradient centrifugation, and high-pressure liquid chromatography on a Shim pack Diol 300 column. On high-pressure liquid chromatography, most of the beta-galactosidase that comigrated with the sialidase on sucrose density gradient centrifugation was removed. The sialidase was purified 3,600-fold from the preparation obtained by Con A-Sepharose adsorption. The enzyme liberated the sialic acid residues from (alpha 2-3) and (alpha 2-6) sialyllactose, colomic acid, fetuin, and transferrin, but not from bovine submaxillary mucin. The enzyme also hydrolyzed gangliosides GM3, GD1a, and GD1b in the presence of sodium cholate as a detergent, but GM1 and GM2 were less susceptible to the enzyme. The optimum pHs for 4-methylumbelliferyl-N-acetylneuraminate, sialyllactose, fetuin, and GM3 lay between 4.0 and 5.0.     

Purification and characterization of a thermotolerant beta-galactosidase from Thermomyces lanuginosus.

A new inducible intracellular beta-galactosidase (EC 3.2.1.23) of the thermophilic fungus Thermomyces lanuginosus was purified by fractional salt precipitation, hydrophobic interaction, and anion exchange chromatography. The first 22 amino acid residues were determined by N-terminal sequencing. Electrophoretic investigations revealed a dimeric enzyme with a molecular mass of 75 to 80 kDa per identical subunit and an isoelectric point of 4.4 to 4.5. The native beta-galactosidase was identified as a glycoprotein by the enzyme-linked immunosorbent assay technique. The beta-galactosidase activity was optimal at pH 6.7 to 7.2, and the enzyme displayed stability between pH 6 and 9. It was completely stable at pH 6.8 and 47 degrees C for 2 h. After 191 h at 50 degrees C, the remaining beta-galactosidase activity of an enzyme fraction after salt precipitation was 58%. The beta-galactosidase hydrolyzed p- and o-NO2-phenyl-beta-D-galactopyranoside, lactose, lactulose, MeOH-beta-D-galactopyranoside, phenyl-beta-D-galactopyranoside, and p-NO2-phenyl-alpha-L-arabinopyranoside. The kinetic constants (Km) measured for p- and o-NO2-phenyl-beta-D-galactopyranoside and beta-lactose were 4.8, 11.3, and 18.2 mM, respectively.     

Purification and properties of an exo-cellulase component of novel type from Trichoderma miride.

An enzyme extract from Cellulase-Onozuka, a commercial product of Trichoderma viride, was fractionated by Amberlite CG-50 column chromatography into three cellulase [EC 3.2.1.4] groups, peaks I to III. A noval enzyme, which has both beta-glucosidase [EC 3.2.1.21] and exo-carboxymethyl-cellulase (exo-CMCase) properties was obtained from peak III by extensive purification throuh consecutive column chromatography. The enzyme was homogeneous on ultracentrifugation, SDS-gel and cellulose acetate film electrophoreses and molecular sieve chromatography on Bio-Gel P-150. The molecular weight of this enzyme was estimated to be 53,000. The enzyme appeared to release cellobiose residues one by one from the nonreducing end of higher cellooligosaccharides and CM-cellulose (CMC), but to release glucosyl residues from reduced cellotriose and beta-cellobioside, resembling a beta-glucosidase in this respect. Furthermore, this exo-CMCase also attacked xylan exo-wise to produce xylobiose moleculaes one by one, but it scarcely attacked insoluble cellulose, except for a cellodextrin apparently rich in amorphous structure.     

Properties of a beta-D-mannosidase from Aspergillus niger

The beta-D-mannosidase (beta-D-mannoside mannohydrolase, EC 3.2.1.25) from culture filtrate of Aspergillus niger has been purified in large amounts by fractionation with (NH4)2SO4 and DEAE-cellulose chromatography. The removal of traces of alpha-D-galactosidase was performed on a Sepharose-epsilon-aminocaproyl-galactosylamine column. The final enzyme preparation (specific activity 188 units) has no other glycosidase activity and is judged homogeneous. The enzyme has a molecular weight of 130 000 +/- 5000 and an isoelectric point of 4.7. The amino acid composition of the enzyme is characterized by high proportion of acidic amino acids and no cysteine residues and a single chain structure of the enzyme is suggested. The enzyme shows maximum activity on p-nitrophenyl-beta-D-mannopyrano-side at pH 3.5 and at 55 degrees C. The presence of 80% of beta-sheet structure in the protein and 20.8% of monosaccharides (Gal : 1.3; Man : 7; GlcNAc : 1) could explain this relative high heat stability (up to 2 h at 55 degrees C). Enzyme activity is inhibited by mannose (Ki = 7.85 mM) and the specificity is examined.     

Purification and properties of galactokinase from Saccharomyces cerevisiae.

Galactokinase (EC 2.7.1.6; ATP:D-galactose-1-phosphotransferase) was purified to homogeneity with a 50% yield from cells of Saccharomyces cerevisiae which were fully induced for the production of the galactose metabolizing enzymes. The purification was accomplished by:(a) ammonium sulfate fractionation, (b) streptomycin sulfate precipitation. (c) DEAE-cellulose chromatography, (d) hydroxylapatite chromatography, and finally (e) Bio-Gel A-0.5 m gel filtration. The resulting preparation of galactokinase was judged to be at least 95% pure by the following criteria: (a) sodium dodecyl sulfate-polyacrylamide gel electrophoresis, (b) ultracentrifuge analysis, (c) nondissociating polyacrylamide gel electrophoresis, and (d) Bio-Gel A-0.5 m gel filtration. The purified enzyme preparation was used to determine the Km values for the two substrates, galactose and ATP, which were found to be 0.60 and 0.15 mM, respectively. Vmax was also determined and found to be 3.35 mmol/h/mg. This corresponds to a turnover rate of 3350 molecules of galactose phosphorylated/min/enzyme molecule. The effect of pH on the galactokinase-catalyzed phosphorylation of galactose was determined; the results showed the pH optimum of the reaction to be in the range of pH 8.0 to 9.0. The enzyme is highly specific for galactose since galactokinase did not appear to phosphorylate any of the other sugars tested at a rate greater than 0.5% of the rate of galactose phosphorylation. Amino acid analysis was performed on the enzyme preparation and the results were used to calculate the partial specific volume (v) of 0.736. The NH2-terminal sequence was determined for the first 3 residues. The molecular weight and subunit composition were determined by ultracentrifugation and polyacrylamide gel electrophoresis under dissociating and nondissociating conditions. The data obtained indicated that galactokinase is a monomeric protein of molecular weight 58,000.     

Purification and partial characterization of cysteine-glutamate transaminase from rat liver.

Cysteine-glutamate transaminase (cysteine aminotransferase; EC 2.6.1.3) has been purified 149-fold to an apparent homogeneity giving a specific activity of 2.09 IU per milligram of protein with an overall yield of 15%. The isolation procedures involve the preliminary separation of a crude rat liver homogenate which was submitted sequentially to ammonium sulfate fractionation, TEAE-cellulose column chromatography, ultrafiltration, and isoelectrofocusing. The final product was homogenous when examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). A minimal molecular weight of 83 500 was determined by Sephadex gel chromatography. The molecular weight as estimated by polyacrylamide gel electrophoresis in the presence of SDS was 84 000. The purified enzyme exhibited a pH optimum at 8.2 with cysteine and alpha-ketoglutarate as substrates. The enzyme is inactivated slowly when kept frozen and is completely inactivated if left at room temperature for 1 h. The enzyme does not catalyze the transamination of alpha-methyl-DL-cysteine, which, when present to a final concentration of 10 mM, exhibits a 23.2% inhibition of transamination of 30 mM of cysteine. The mechanism apparently resembles that of aspartate-glutamate transaminase (EC 2.6.1.1) in which the presence of a labile hydrogen on the alpha-carbon in the substrate is one of the strict requirements.     

Purification and characterisation of an inducible beta-galactosidase from Corynebacterium murisepticum

The beta-galactosidase (EC 3.2.1.32) of Corynebacterium murisepticum (inducible by lactose and galactose) was purified by successive column chromatography on Sephadex G-200, DEAE-Sephadex A-50 and DEAE-cellulose (DE52). The enzyme was found to be a dimer of identical subunits of molecular mass 100,000 daltons. The Km values of the enzyme for the substrates lactose and o-nitrophenyl-beta-D-galactopyranoside (ONPG) are 16.7 mM and 4.4 mM, respectively, indicating, its low affinity for the substrates. The Ouchterlony immunodiffusion method exhibited immunological homogeneity of the enzyme preparation. The catalytic site of the enzyme does not take part in antigen-antibody reaction.     

Intracellular distribution of beta-galactosidases in mucosal cells from hog small intestine.

1. Intracellular distribution of three types of beta-galactosidases (beta-D-galactoside galactohydrolase EC 3.2.1.12) i.e. hetero beta-galactosidase, lactase and acid beta-galactosidase, was studied by examining the properties of subcellular fractions isolated by a systematic fractionation of mucosal cells of the small intestine of the hog. Localization of hetero beta-galactosidase in cytosol could be shown. 2. Localization of lactase in the brush borders was shown by analyzing the purified brush borders prepared separately. 3. To domonstrate the lysosomal localization of acid belta-galactosidase, lysosomes were purified separately and their extract was chromatographed on a hydroxylapatite column. The activities of various enzymes in the purified lysosomes as well as in the intermediary fractions obtained during lysosome purification and the pattern of the hydroxylapatite chromatography led us to conclude that acid beta-galactosidase is a lysosomal enzyme.     

Pyridoxal phosphate-sensitized photoinactivation of glutamate decarboxylase from Clostridium perfringens

1. l-Glutamate decarboxylase (EC 4.1.1.15) from Clostridium perfringens was inactivated by exposure to visible light at pH6.2. 2. Inactivation does not occur at pH4.6 or in the absence of bound pyridoxal phosphate. 3. On prolonged photo-oxidation six histidine residues per molecule of enzyme were destroyed. 4. The loss of six cysteine residues per molecule occurred both in irradiated samples and in controls oxygenated in the dark. 5. This dark-oxidation of cysteine residues is apparently required before the photo-oxidation process. 6. The absorbance, fluorescence and circular-dichroism properties of the enzyme as well as its elution volume during Sephadex gel-filtration were unaffected by prolonged irradiation. 7. However, an apparently homogeneous product of photo-oxidation could be separated from the control enzyme by ion-exchange chromatography. 8. The K(m) for l-glutamate was unchanged in an irradiated sample retaining 22% of control activity. 9. These data and the catalytic role of imidazole residues at the active sites of amino acid decarboxylases are discussed.     

Purification and properties of galactokinase from pig liver

1. Galactokinase has been purified from the liver of young pigs by high-speed centrifugation, chromatography on Sephadex G-100 and DEAE-cellulose, and ammonium sulphate fractionation. 2. The enzyme preparation has a specific activity of 10-18mumoles of galactose phosphorylated/mg. of protein/min. at 37 degrees and has been purified 400-fold from the liver supernatant. 3. Purified liver galactokinase has Michaelis constants of 1x10(-4)-3x10(-4)m for galactose and 2x10(-4)m for ATP-Mg(2+), and the enzyme reaction produces equimolar amounts of galactose 1-phosphate and ADP. 4. Galactokinase phosphorylates 2-deoxygalactose and galactosamine in addition to galactose, has a pH optimum of 7.8, a Q(10) of 2, and is stimulated by cysteine and other thiols. 5. With the exception of substrate specificity, the properties of liver galactokinase are similar to galactokinase purified from yeast and Escherichia coli.     

Some properties of galactokinase in developing rat liver

1. The nature of the galactokinase present in the livers of foetal, newborn and adult rats was examined by the application of several separation procedures and by measurement of a range of kinetic parameters. 2. No evidence of enzyme heterogeneity at any stage of development was found during gel filtration on Sephadex G-100, column chromatography on DEAE-cellulose or a variety of electrophoretic procedures. 3. The K(m) values, inhibition characteristics and other kinetic parameters appear to remain constant during development. 4. Rat liver galactokinase activity does not adapt to dietary changes in either the adult or the newborn rat; hence it is unlikely that the presence of galactose in milk controls the enzymic activity profile during development. 5. On the present evidence it is concluded that only one form of galactokinase is present in rat liver and that the enzymic activity is controlled by non-dietary factors.     

Neutral sphingomyelinase from human urine. Purification and preparation of monospecific antibodies

A neutral sphingomyelinase which cleaves phosphorylcholine from sphingomyelin at a pH optima of 7.4 was purified 440-fold to apparent homogeneity from normal human urine concentrate employing Sephadex G-75 column chromatography, preparative isoelectric focusing, and sphingosylphospholcholine CH-Sepharose column chromatography. The enzyme is composed of a single polypeptide whose apparent molecular weight is 92,000. Analytical isoelectric focusing revealed that the pI of this enzyme is 6.5. Purified neutral sphingomyelinase was devoid of beta-galactosidase and beta-N-acetylglucosaminidase activity originally present in the urine concentrate. The purified neutral sphingomyelinase (N-SMase) had low levels of phospholipase A1 and A2 activity when phosphatidylcholine was used as a substrate and detergents were included in the assay mixture. However, it had no phospholipase activity toward phosphatidylglycerol and sphingomyelin at pH 4.5 irrespective of the presence or absence of detergents. Monospecific polyclonal antibodies raised against N-SMase immunoprecipitated approximately 70% of N-SMase activity from urine, human kidney proximal tubular cells, and partially purified membrane-bound N-SMase from these cells. Western immunoblot assays revealed that the monospecific polyclonal antibody against urinary N-SMase recognized both the urinary N-SMase and the membrane-bound N-SMase. Because this enzyme is distinct biochemically and immunologically as compared to acid sphingomyelinase (EC 3.1.4.12), we would like to assign it an enzyme catalog number of EC 3.1.4.13. The availability of N-SMase and corresponding antibody will be useful in studying various aspects of this enzyme in biological systems.     

Phosphoenolpyruvate carboxylase of Escherichia coli K-12. N- and C-terminal sequences and tentative assignment of the catalytically essential cysteine residue

The N- and C-terminal amino acid sequences of phosphoenolpyruvate carboxylase [EC 4.1.1.31] from Escherichia coli K-12 were determined to establish the primary structure deduced from the nucleotide sequence of the cloned gene for the enzyme (Fujita, N., Miwa, T., Ishijima, S., Izui, K., & Katsuki, H. (1984) J. Biochem. 95, 909-916). As predicted from the nucleotide sequence, two polypeptides were produced upon treatment with hydroxylamine, which specifically cleaves the Asn-Gly bond, and their amino acid compositions were also in accordance with those predicted. The tryptic peptides which contained cysteine residues labeled with a fluorescent reagent, N-[7-(dimethylamino)-4-methylcoumarinyl]maleimide, were isolated by high-performance liquid chromatography and partially sequenced. All of them could be assigned on the deduced primary structure. The modified cysteine residues were Cys-157, Cys-385, Cys-458, Cys-568, Cys-665, and Cys-754. Furthermore, the essential cysteine residue which is presumably located at or near the active site was tentatively identified as Cys-568, since it was consistently protected against the modification by 2-phospholactate, a substrate analog.     

Cloning, expression, and purification of a recombinant cold-adapted beta-galactosidase from antarctic bacterium Pseudoalteromonas sp. 22b

The gram-negative antarctic bacterium Pseudoalteromonas sp. 22b, isolated from the alimentary tract of krill Thyssanoessa macrura, synthesizes an intracellular cold-adapted beta-galactosidase. The gene encoding this beta-galactosidase has been PCR amplified, cloned, expressed in Escherichia coli, purified, and characterized. The enzyme is active as a homotetrameric protein, and each monomer consists of 1028 amino acid residues. The enzyme was purified to homogeneity (50% recovery of activity) by using the fast, two-step procedure, including affinity chromatography on PABTG-Sepharose. Enzymatic properties of the recombinant protein are identical to those of native Pseudoalteromonas sp. 22b beta-galactosidase. The enzyme is cold-adapted and at 10 degrees C retains 20% of maximum activity. The purified enzyme displayed maximum activity close to 40 degrees C and at pH of 6.0-8.0. PNPG was its preferred substrate (58% higher activity than against ONPG). The enzyme was particularly thermolabile, losing all activities within 10 min at 50 degrees C. The hydrolysis of lactose in a milk assay revealed that 90% of milk lactose was hydrolyzed during 6 h at 30 degrees C and during 28 h at 15 degrees C. Because of its attributes, the recombinant Pseudoalteromonas sp. 22b beta-galactosidase could be applied at refrigeration temperatures for production of lactose-reduced dairy products.     

Biochemical and immunological studies of purified mouse beta-galactosidase.

Beta-Galactosidase (EC 3.2.1.23) has been purified from the livers of C57BL/6J mice. The enzyme migrated as a single band of protein on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular weight of the denatured and reduced enzyme was 63,000. The native form of beta-galactosidase appeared to be a tetramer of 240,000 at pH 5.0, which was reversibly dissociated at alkaline pH to a dimer with apparent molecular weight of 113,000. Multiple charge isomers of beta-galactosidase were resolved by polyacrylamide gel electrophoresis and ion exchange chromatography. Treatment of beta-galactosidase with neuraminidase markedly reduced its electrophoretic mobility. Purified enzyme as well as crude liver extract hydrolyzed p-nitrophenyl-beta-D-fucoside at one-tenth the rate of hydrolysis of the beta-galactoside. Antiserum to the purified enzyme precipitated the major portion of beta-galactosidase activity of mouse liver, brain, and kidney. This antiserum cross-reacts with beta-galactosidases from rat and Chinese hamster, but not with human, porcine, or bovine beta-galactosidase.     

Purification and characterization of a sea squirt beta-galactosidase

A beta-galactosidase was extracted from the internal organs of a sea squirt, Styela plicata, and purified 959-fold, with an 18% yield, by successive gel chromatography, anion-exchange chromatography, chromatofocusing, and affinity chromatography on a Con A-Sepharose column. The purified enzyme was fairly homogeneous, as judged on disc PAGE, SDS-PAGE, and gel chromatography on a Sephadex G-200 column. The molecular weight of the enzyme was estimated to be 77,000 and 75,000 by gel chromatography and SDS-PAGE, respectively, and its isoelectric point was determined to be 4.9 by the isoelectric focusing method. The enzyme was substantially stable in the pH range of 3.5 to 7.5, the optimum pH being 4.0. The enzyme was significantly inhibited by 9 mM HgCl2 and 9 mM DFP, while the inhibition by 0.9% PCMB was only 60% at 0 degrees C for 30 min. The purified beta-galactosidase apparently liberated galactose from a sea squirt antigen (H-antigen), two allergenically active glycopeptides (Gp-1 and Gp-2) derived from another sea squirt antigen (Gi-rep), asialo-ovomucoid glycopeptide, asialo-fetuin glycopeptide, GA1, CDH, and an ABEE-derivative (Gal beta 1----3ThrNAc-ABEE) of Gal beta 1----3GalNAc-ol isolated from bovine submaxillary gland mucin.