scholarly journals (335) Purification and Characterization of ADP-glucose Pyrophosphorylase from Apple Leaves

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1083C-1083
Author(s):  
Rui Zhou ◽  
Lailiang Cheng
Keyword(s):  
Enzyme Activity ◽  
Thermal Inactivation ◽  
Specific Activity ◽  
Purification And Characterization ◽  
Apple Leaves ◽  
Apparent Homogeneity ◽  
Adp Glucose Pyrophosphorylase ◽  
High Concentrations ◽  
Dual Functions

Apple leaf ADP-glucose pyrophosphorylase was purified over 1400-fold to apparent homogeneity with a specific activity of 58.9 units per mg of protein. The enzyme was activated by 3-phosphoglycerate (PGA) and inhibited by inorganic phosphate (Pi) in the ADPG synthesis direction. In the pyrophosphorolysis direction, however, high concentrations of PGA (>2.5 mm) inhibited the enzyme activity. The enzyme was resistant to thermal inactivation with a T0.5 (temperature at which 50% of the enzyme activity is lost after 5 min of incubation) of 52 °C. Incubation with 2 mm PGA or 2 mm Pi increased T0.5 to 68 °C. Incubation with 2 mm dithiothreitol (DTT) decreased T0.5 to 42 °C, whereas inclusion of 2 mm PGA in the DTT incubation maintained T0.5 at 52 °C. DTT-induced decrease in thermal stability was accompanied by monomerization of the small subunits. Presence of PGA in the DTT incubation did not alter the monomerization of the small subunits of the enzyme induced by DTT. These findings indicate that the binding of PGA may have dual functions in regulating apple leaf AGPase activity—activating the enzyme and rendering the enzyme with a conformation more stable to thermal inactivation.

Binding of 3-phosphoglycerate leads to both activation and stabilisation of ADP-glucose pyrophosphorylase from apple leaves

2005 ◽  
Vol 32 (9) ◽  
pp. 839
Author(s):  
Rui Zhou ◽  
Lailiang Cheng
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Enzyme Activity ◽  
Inorganic Phosphate ◽  
Thermal Inactivation ◽  
Specific Activity ◽  
Apple Leaves ◽  
Apparent Homogeneity ◽  
Adp Glucose Pyrophosphorylase ◽  
High Concentrations

Apple leaf ADP-glucose pyrophosphorylase was purified 1436-fold to apparent homogeneity with a specific activity of 58.9 units mg–1. The enzyme was activated by 3-phosphoglycerate (PGA) and inhibited by inorganic phosphate (Pi) in the ADPG synthesis direction. In the pyrophosphorolytic direction, however, high concentrations of PGA (> 2.5 mm) inhibited the enzyme activity. The enzyme was resistant to thermal inactivation with a T0.5 (temperature at which 50% of the enzyme activity is lost after 5 min incubation) of 52°C. Incubation with 2 mm PGA or 2 mm Pi increased T0.5 to 68°C. Incubation with 2 mm dithiothreitol (DTT) decreased T0.5 to 42°C, whereas inclusion of 2 mm PGA in the DTT incubation maintained T0.5 at 52°C. DTT-induced decrease in thermal stability was accompanied by monomerisation of the small subunits. Presence of PGA in the DTT incubation did not alter the monomerisation of the small subunits of the enzyme induced by DTT. These findings indicate that binding of PGA renders apple leaf AGPase with a conformation that is not only more efficient in catalysis but also more stable to heat treatment. The physiological significance of the protective effect of PGA on thermal inactivation of AGPase is discussed.

scholarly journals Purification and characterization of human platelet glutathione-S- transferase

Blood ◽  
1986 ◽  
Vol 67 (6) ◽  
pp. 1595-1599
Author(s):  
J Loscalzo ◽  
J Freedman
Keyword(s):  
Specific Activity ◽  
Human Platelet ◽  
Reduced Glutathione ◽  
Human Platelets ◽  
Glutathione S Transferase ◽  
Purification And Characterization ◽  
Ph Optimum ◽  
Complete Purification ◽  
High Concentrations

A glutathione-S-transferase was isolated and purified to homogeneity from human platelets. With a combination of ammonium sulfate fractionation and chromatographic methods, 0.2 mg of pure enzyme was obtained from 9 X 10(11) platelets with a 12% recovery. The purified enzyme had a specific activity of 7.5 U per milligram, representing an approximately 1,100-fold purification. The enzyme was found to be anionic, with an isoelectric point of 4.6. With reduced glutathione as a co-substrate, platelet glutathione-S-transferase was most active with the synthetic substrate, 1-chloro-2,4-dinitrobenzene, less active with 1,2-dichloro-4-nitrobenzene, and essentially inactive with nitroglycerin and 1,2-epoxy-3-(p-nitrophenoxy)-propane. The pH optimum for activity with glutathione and 1-chloro-2,4-dinitrobenzene was 7.0. Indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyindole-3-acetic acid), a chlorobenzene derivative, noncompetitively inhibited human platelet glutathione-S-transferase with an apparent KI of 0.23 mmol/L. This study represents the first complete purification and characterization of a glutathione-S-transferase from platelets. The presence of this enzyme in the platelet, within which high concentrations of reduced glutathione coexist, suggests the potential importance of the platelet in detoxification reactions and in the synthesis of the glutathione adducts of leukotriene metabolism.

scholarly journals Purification and Characterization of a Polyextremophilicα-Amylase from an Obligate HalophilicAspergillus penicillioidesIsolate and Its Potential for Souse with Detergents

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Imran Ali ◽  
Ali Akbar ◽  
Mohammad Anwar ◽  
Sehanat Prasongsuk ◽  
Pongtharin Lotrakul ◽  
...  
Keyword(s):  
Specific Activity ◽  
Amylase Activity ◽  
Gel Filtration ◽  
Soluble Starch ◽  
Ammonium Sulfate Precipitation ◽  
Purification And Characterization ◽  
Apparent Homogeneity ◽  
Sds Page ◽  
Good Potential

An extracellularα-amylase from the obligate halophilicAspergillus penicillioidesTISTR3639 strain was produced and enriched to apparent homogeneity by ammonium sulfate precipitation and Sephadex G100 gel filtration column chromatography. The mass of the purified amylase was estimated to be 42 kDa by SDS-PAGE. With soluble starch as the substrate it had a specific activity of 118.42 U·mg−1andVmax⁡andKmvalues of 1.05 µmol·min−1·mg−1and 5.41 mg·mL−1, respectively. The enzyme was found to have certain polyextremophilic characteristics, with an optimum activity at pH 9, 80°C, and 300 g·L−1NaCl. The addition of CaCl2at 2 mM was found to slightly enhance the amylase activity, while ZnCl2, FeCl2, or EDTA at 2 mM was strongly or moderately inhibitory, respectively, suggesting the requirement for a (non-Fe2+or Zn2+) divalent cation. The enzyme retained more than 80% of its activity when incubated with three different laundry detergents and had a better performance compared to a commercial amylase and three detergents in the presence of increasing NaCl concentrations up to 300 g·L−1. Accordingly, it has a good potential for use as anα-amylase in a low water activity (high salt concentration) and at high pH and temperatures.

scholarly journals Purification and characterization of rat intestinal peroxidase. Its activity towards 2-t-butyl-4-methoxyphenol (BHA)

1988 ◽  
Vol 250 (2) ◽  
pp. 501-507 ◽  
Author(s):  
M Valoti ◽  
L Della Corte ◽  
K F Tipton ◽  
G Sgaragli
Keyword(s):  
Specific Activity ◽  
Maximum Velocity ◽  
Purification And Characterization ◽  
Reaction Progress ◽  
Reversible Aggregation ◽  
Aggregation Behaviour ◽  
Apparent Homogeneity ◽  
Specificity Constant ◽  
Km Value

Impure preparations of rat intestinal peroxidase were shown to aggregate at low ionic strengths and to disaggregate at higher values. This aggregation was accompanied by a decrease in specific activity, which could lead to hysteretic behaviour of reaction progress curves. Advantage was taken of this reversible aggregation to obtain a relatively pure extract, which was subsequently purified to apparent homogeneity by affinity chromatography on concanavalin A-Sepharose followed by hydrophobic chromatography. The purified enzyme did not show the ionic-strength-dependent aggregation behaviour, behaving as a monomer of Mr 50,000. The purified enzyme was shown to catalyse the peroxidatic conversion of the commonly used antioxidant 2-t-butyl-4-methoxyphenol (butylated hydroxyanisole, BHA) to form 3,3′-di-t-butyl-2,2′-dihydroxy-5,5′-dimethoxybiphenyl, with a Km value of 176 microM and a maximum velocity of 8 mumol/min per mg. The specificity constant, kcat./Km, for this substrate was similar to that shown towards the substrate guaiacol.

scholarly journals Overproduction, purification and characterization of M.EcoHK31I, a bacterial methyltransferase with two polypeptides

1996 ◽  
Vol 314 (1) ◽  
pp. 321-326 ◽  
Author(s):  
Kai-Fai LEE ◽  
Yen-Chywan LIAW ◽  
Pang-Chui SHAW
Keyword(s):  
Initial Rate ◽  
Specific Activity ◽  
Overlapping Genes ◽  
Purification And Characterization ◽  
Native Molecular Mass ◽  
Apparent Homogeneity ◽  
Molecular Masses ◽  
Chromatographic Media ◽  
Lambda Dna

The two overlapping genes coding for EcoHK31I methyltransferase have previously been cloned, sequenced and expressed [Lee, Kam and Shaw (1995) Nucleic Acids Res. 23, 103–108]. Here we describe protocols developed to purify polypeptides α and β together or separately, to apparent homogeneity by various chromatographic media. M.EcoHK31I is a heterodimer with a native molecular mass of 61 kDa. Its specific activity towards non-methylated lambda DNA was 3.0×105 units per mg of protein. The respective denatured molecular masses of polypeptides α and β were 38 and 23 kDa, and their pI values were 8.7 and 6.8. Initial rate kinetic parameters of the native enzyme were 2.0 nM, 0.58 μM and 3 min-1 for KmDNA, KmAdoMet and kcat. respectively, where AdoMet stands for S-adenosyl-L-methionine. Fully active enzyme was reconstituted by co-purifying the two separately synthesized polypeptides, and activity assays confirmed our previous finding that two polypeptides were needed to methylate substrate DNA.

scholarly journals Expression, purification, and characterization of recombinant human glutamine synthetase

1997 ◽  
Vol 328 (1) ◽  
pp. 159-163 ◽  
Author(s):  
D. Chad LISTROM ◽  
Hiroki MORIZONO ◽  
S. Basavapatna RAJAGOPAL ◽  
T. Mark McCANN ◽  
Mendel TUCHMAN ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Thermal Inactivation ◽  
Colorimetric Assay ◽  
Expression System ◽  
Purification And Characterization ◽  
X Ray Crystallography ◽  
Apparent Homogeneity ◽  
A Subunit ◽  
Radioactive Assay

A bacterial expression system has been engineered for human glutamine synthetase (EC 6.3.1.2) that produces approximately 60 mg of enzyme (20% of the bacterial soluble protein) and yields approx. 8 mg of purified enzyme per litre of culture. The recombinant enzyme was purified 5-fold to apparent homogeneity and characterized. It has a subunit molecular mass of approx. 45000 Da. The Vmax value obtained using a radioactive assay with ammonia and L-[G-3H]glutamic acid as substrates was 15.9 μmol/min per mg, 40% higher than that obtained in the colorimetric assay (9.9 μmol/min per mg) with hydroxylamine replacing ammonia as a substrate. Km values for glutamate were 3.0 mM and 3.5 mM, and for ATP they were 2.0 mM and 2.9 mM for the radioactive and spectrophotometric assays respectively. The Km for ammonia in the radioactive assay was 0.15 mM. The midpoint of thermal inactivation was 49.7 °C. Hydroxylamine, Mg(II) and Mg(II)-ATP stabilized the enzyme against thermal inactivation, whereas ATP promoted inactivation. The pure enzyme is stable for several months in storage and provides a source for additional studies, including X-ray crystallography.

scholarly journals Purification and Characterization of a Carbonyl Reductase from Human Liver, which is Competent in the Reduction of 6-Pyruvoyl-Tetrahydropterin

Pteridines ◽  
1989 ◽  
Vol 1 (4) ◽  
pp. 189-198 ◽  
Author(s):  
Petra Steinerstauch ◽  
Yoshitomo Sawada ◽  
Walter Leimbacher ◽  
Sandro Ghisla ◽  
Hans-Christoph Curtius
Keyword(s):  
Human Liver ◽  
Specific Activity ◽  
Polyclonal Antibodies ◽  
Potassium Phosphate ◽  
Side Chain ◽  
Purification And Characterization ◽  
Single Polypeptide Chain ◽  
Apparent Homogeneity ◽  
Single Polypeptide

Summary An enzyme which reduces 6-pyruvoyl-tetrahydropterin has been purified to apparent homogeneity from human liver. It consists of a single polypeptide chain with a molecular weight of 35 kDa, has an isoelectric point of 5.9 ± 0.1 and contains no glycosyl residues. The pure enzyme has a specific activity of 450 mU/mg protein at pH 7.0 in 10 mM potassium phosphate buffer. It converts 6-pyruvoyl-tetrahydropterin to 6-lactoyltetrahydropterin by transfer of the pro 4R-hydrogen of NADPH to form the side chain -OH at position C(2') of the substrate. Km values are 1.8 J..lM for 6-pyruvoyl-tetrahydropterin and 5.5 J..lM for NADPH. Polyclonal antibodies raised against the purified enzyme recognize 6-pyruvoyl-tetrahydropterin reductase in Western blot and ELISA but do not cross-react with human sepiapterin reductase. The enzyme appears to be identical with aldose reductase.

scholarly journals Purification and characterization of human platelet glutathione-S- transferase

Blood ◽  
1986 ◽  
Vol 67 (6) ◽  
pp. 1595-1599 ◽  
Author(s):  
J Loscalzo ◽  
J Freedman
Keyword(s):  
Specific Activity ◽  
Human Platelet ◽  
Reduced Glutathione ◽  
Human Platelets ◽  
Glutathione S Transferase ◽  
Purification And Characterization ◽  
Ph Optimum ◽  
Complete Purification ◽  
High Concentrations

Abstract A glutathione-S-transferase was isolated and purified to homogeneity from human platelets. With a combination of ammonium sulfate fractionation and chromatographic methods, 0.2 mg of pure enzyme was obtained from 9 X 10(11) platelets with a 12% recovery. The purified enzyme had a specific activity of 7.5 U per milligram, representing an approximately 1,100-fold purification. The enzyme was found to be anionic, with an isoelectric point of 4.6. With reduced glutathione as a co-substrate, platelet glutathione-S-transferase was most active with the synthetic substrate, 1-chloro-2,4-dinitrobenzene, less active with 1,2-dichloro-4-nitrobenzene, and essentially inactive with nitroglycerin and 1,2-epoxy-3-(p-nitrophenoxy)-propane. The pH optimum for activity with glutathione and 1-chloro-2,4-dinitrobenzene was 7.0. Indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyindole-3-acetic acid), a chlorobenzene derivative, noncompetitively inhibited human platelet glutathione-S-transferase with an apparent KI of 0.23 mmol/L. This study represents the first complete purification and characterization of a glutathione-S-transferase from platelets. The presence of this enzyme in the platelet, within which high concentrations of reduced glutathione coexist, suggests the potential importance of the platelet in detoxification reactions and in the synthesis of the glutathione adducts of leukotriene metabolism.

scholarly journals Purification and characterization of an acetyl xylan esterase produced by Streptomyces lividans

1996 ◽  
Vol 319 (3) ◽  
pp. 881-886 ◽  
Author(s):  
Claude DUPONT ◽  
Nicole DAIGNEAULT ◽  
François SHARECK ◽  
Rolf MOROSOLI ◽  
Dieter KLUEPFEL
Keyword(s):  
Enzyme Activity ◽  
Culture Filtrate ◽  
Specific Activity ◽  
Streptomyces Lividans ◽  
Birchwood Xylan ◽  
Acetyl Xylan Esterase ◽  
Purification And Characterization ◽  
Acetyl Group ◽  
Assay Conditions

The acetyl xylan esterase cloned homologously from Streptomyces lividans [Shareck, Biely, Morosoli and Kluepfel (1995) Gene 153, 105–109] was purified from culture filtrate of the overproducing strain S. lividans IAF43. The secreted enzyme had a molecular mass of 34 kDa and a pI of 9.0. Under the assay conditions with chemically acetylated birchwood xylan the kinetic constants of the enzyme were: specific activity, 715 units/mg, Km 7.94 mg/ml and Vmax 1977 units/mg. Optimal enzyme activity was obtained at 70 °C and pH 7.5. Hydrolysis assays with different acetylated substrates showed that the enzyme is specific for deacetylating the O-acetyl group of polysaccharides and is devoid of N-deacetylation activity. Sequential hydrolysis shows that its action is essential for the complete degradation of acetylated xylan by the xylanases of S. lividans.

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