scholarly journals Purification and characterization of aspartate aminotransferase from the halophile archaebacterium Haloferax mediterranei

1991 ◽  
Vol 278 (1) ◽  
pp. 149-154 ◽  
Author(s):  
F J G Muriana ◽  
M C Alvarez-Ossorio ◽  
A M Relimpio
Keyword(s):  
Aspartate Aminotransferase ◽  
Maximum Activity ◽  
Purification And Characterization ◽  
Scanning Calorimetry ◽  
Haloferax Mediterranei ◽  
First Order Kinetics ◽  
Low Salt ◽  
Titration Data ◽  
Ph Range

Aspartate aminotransferase from the archaebacterium Haloferax mediterranei was purified and found to be homogeneous. An average Mr of 66,000 was estimated. The native halophilic transaminase exhibited no maximum absorption at 410 nm, which indicates that the apo form is obtained by our purification procedure, and the molar absorption coefficient at 275 nm in 3.5 M-KCl (pH 7.8) was found to be 78.34 mM-1.cm-1. Plots of titration data show that 1 mol of halophilic aspartate aminotransferase binds 2 mol of pyridoxal 5′-phosphate. The halophilic transaminase behaved as a dimer with two similar subunits and had a maximum activity in the pH range 7.6-7.9 and at 65 degrees C in 3.5 M-KCl. By differential scanning calorimetry, the denaturation temperature of the halophilic holo- and apo-transaminase was determined to be 78.5 and 68.0 degrees C respectively at 3.3 M-KCl (pH 7.8). At low salt concentration the halophilic transaminase was inactivated, following first-order kinetics. The Km values for 2-oxoglutarate and L-aspartate, in 3 M-KCl (pH 7.8), were 0.75 mM and 12.6 mM respectively.

scholarly journals Further thermal characterization of an aspartate aminotransferase from a halophilic organism

1994 ◽  
Vol 298 (2) ◽  
pp. 465-470 ◽  
Author(s):  
F J G Muriana ◽  
M C Alvarez-Ossorio ◽  
A M Relimpio
Keyword(s):  
Thermal Stability ◽  
Aspartate Aminotransferase ◽  
Thermal Inactivation ◽  
Hydrophobic Interactions ◽  
Thermal Characterization ◽  
Haloferax Mediterranei ◽  
First Order Kinetics ◽  
Effects Of Temperature ◽  
Thermal Stability Of

Aspartate aminotransferase (AspAT, EC 2.6.1.1) from the halophilic archaebacterium Haloferax mediterranei was purified [Muriana, Alvarez-Ossorio and Relimpio (1991) Biochem. J. 278, 149-154] and further characterization of the effects of temperature on the activity and stability of the halophilic AspAT were carried out. The halophilic transaminase is most active at 65 degrees C and stable at high temperatures, under physiological or nearly physiological conditions (3.5 M KCl, pH 7.8). Thermal inactivation (60-85 degrees C) of the halophilic AspAT followed first-order kinetics, 2-oxoglutarate causing a shift of the thermal inactivation curves to higher temperatures. The salt concentration affected the thermal stability of the halophilic transaminase at 60 degrees C, suggesting that disruption of hydrophobic interactions may play an important role in the decreased thermal stability of the enzyme.

Effect of Salt on the Activity and Stability of Aspartate Aminotransferase from the Halophilic Archaebacterium Haloferax mediterranei

1992 ◽  
Vol 47 (5-6) ◽  
pp. 375-381 ◽  
Author(s):  
Francisco J. G. Muriana ◽  
María C. Alvarez-Ossorio ◽  
María M. Sánchez-Garcés ◽  
Francisco F. de la Rosa ◽  
Angel M. Relimpio
Keyword(s):  
Aspartate Aminotransferase ◽  
Electrostatic Interactions ◽  
Enzyme Stability ◽  
Active Form ◽  
Maximum Activity ◽  
Haloferax Mediterranei ◽  
Significant Difference ◽  
Low Salt ◽  
High Concentrations ◽  
Partial Activity

The aspartate aminotransferase from Haloferax mediterranei, which is in the cell mainly as apoenzyme, requires high concentrations of salt for both activity and stability. The maximum activity is reached with 3.5 ᴍ KCl in the assay. The effect of different cations and anions has been studied using several types of salts. Monovalent cations show a significant difference in effectiveness of promoting the activity with the following order: K+ > Rb+ > Na+ > NH4+. Mg++ and polyvalent cations with organic character cause partial activity with maximum effectiveness at 0.1 ᴍ, an inhibition at higher concentration is observed. Anions, added as potassium salts, promote enzyme activity with the following order: Cl- > NO3- > I- > SCN-. Like activity, the enzyme stability depends on salt concentrations. Incubation of the enzyme with a low salt concentration leads to inactivation following pseudofirst order kinetics. The inactivated enzyme is partially reactivated by high concentrations of KC1 following second order kinetics. Taking into account the dimeric structure of this enzyme, high concentrations of salt could stabilize the dimer, which is the active form. The salt effects on halophile aspartate am inotransferase are discussed considering hydrophobic and electrostatic interactions.

scholarly journals Characterization of a Robust and pH-Stable Tannase from Mangrove-Derived Yeast Rhodosporidium diobovatum Q95

Marine Drugs ◽  
2020 ◽  
Vol 18 (11) ◽  
pp. 546
Author(s):  
Jie Pan ◽  
Ni-Na Wang ◽  
Xue-Jing Yin ◽  
Xiao-Ling Liang ◽  
Zhi-Peng Wang
Keyword(s):  
Gallic Acid ◽  
Tannic Acid ◽  
Specific Activity ◽  
Maximum Activity ◽  
Sds Page ◽  
Rhodosporidium Diobovatum ◽  
Bacteria And Fungi ◽  
Ph Range ◽  
First Time

Tannase plays a crucial role in many fields, such as the pharmaceutical industry, beverage processing, and brewing. Although many tannases derived from bacteria and fungi have been thoroughly studied, those with good pH stabilities are still less reported. In this work, a mangrove-derived yeast strain Rhodosporidium diobovatum Q95, capable of efficiently degrading tannin, was screened to induce tannase, which exhibited an activity of up to 26.4 U/mL after 48 h cultivation in the presence of 15 g/L tannic acid. The tannase coding gene TANRD was cloned and expressed in Yarrowia lipolytica. The activity of recombinant tannase (named TanRd) was as high as 27.3 U/mL. TanRd was purified by chromatography and analysed by SDS-PAGE, showing a molecular weight of 75.1 kDa. The specific activity of TanRd towards tannic acid was 676.4 U/mg. Its highest activity was obtained at 40 °C, with more than 70% of the activity observed at 25–60 °C. Furthermore, it possessed at least 60% of the activity in a broad pH range of 2.5–6.5. Notably, TanRd was excellently stable at a pH range from 3.0 to 8.0; over 65% of its maximum activity remained after incubation. Besides, the broad substrate specificity of TanRd to esters of gallic acid has attracted wide attention. In view of the above, tannase resources were developed from mangrove-derived yeasts for the first time in this study. This tannase can become a promising material in tannin biodegradation and gallic acid production.

Purification and characterization of catalase HPII from Escherichia coli K12

1986 ◽  
Vol 64 (7) ◽  
pp. 638-646 ◽  
Author(s):  
Peter C. Loewen ◽  
Jacek Switala
Keyword(s):  
Escherichia Coli ◽  
Sodium Dodecyl ◽  
Purification And Characterization ◽  
Unusual Structure ◽  
Escherichia Coli K12 ◽  
Molecular Weights ◽  
Ph Range ◽  
Heme Cofactor ◽  
Native Molecular Weight

Catalase (hydroperoxidase II or HPII) of Escherichia coli K12 has been purified using a protocol that also allows the purification of the second catalase HPI in large amounts. The purified HPII was found to have equal amounts of two subunits with molecular weights of 90 000 and 92 000. Only a single 92 000 subunit was present in the immunoprecipitate created when HPII antiserum was added directly to a crude extract, suggesting that proteolysis was responsible for the smaller subunit. The apparent native molecular weight was determined to be 532 000, suggesting a hexamer structure for the enzyme, an unusual structure for a catalase. HPII was very stable, remaining maximally active over the pH range 4–11 and retaining activity even in a solution of 0.1% sodium dodecyl sulfate and 7 M urea. The heme cofactor associated with HPII was also unusual for a catalase, in resembling heme d (a2) both spectrally and in terms of solubility. On the basis of heme-associated iron, six heme groups were associated with each molecule of enzyme or one per subunit.

scholarly journals Purification and Characterization of Aspartate Aminotransferase Isoenzymes from Rice Bran

1993 ◽  
Vol 57 (12) ◽  
pp. 2074-2080 ◽  
Author(s):  
Toshiharu Yagi ◽  
Masayuki Sako ◽  
Shinya Moriuti ◽  
Masafumi Shounaka ◽  
Kazunari Masaki ◽  
...  
Keyword(s):  
Rice Bran ◽  
Aspartate Aminotransferase ◽  
Purification And Characterization

scholarly journals Purification and characterization of the heat-stable serine proteinase from Thermomonospora fusca YX

1987 ◽  
Vol 246 (2) ◽  
pp. 511-517 ◽  
Author(s):  
T W Gusek ◽  
J E Kinsella
Keyword(s):  
Thermal Stability ◽  
Ionic Strength ◽  
Serine Proteinase ◽  
Maximum Activity ◽  
Exchange Chromatography ◽  
Cation Exchange Chromatography ◽  
Purification And Characterization ◽  
Thermomonospora Fusca ◽  
Heat Stable

The proteinase secreted from Thermomonospora fusca YX grown on cellulose was purified by (NH4)2SO4 fractionation and cation-exchange chromatography. The isolated proteinase readily hydrolysed several proteins and demonstrated activity towards casein from 35 to 95 degrees C (at pH 8.0) with maximum activity at 80 degrees C. It exhibited broad pH and ionic-strength optima centered at pH 9.0 and 0.2 M-NaCl respectively, and it retained high activity in the presence of 2% (w/v) SDS, 20 mM-dithiothreitol and 1.0 M-NaCl. The proteinase, which was fully inhibited by phenylmethanesulphonyl fluoride, had an Mr of 14,500 and an isoelectric point at 9.21. A measurement of proteinase thermal stability demonstrated a T50% (15 min) of 85 degrees C at pH 4.5.

Purification and Characterization of Limit Dextrinase from Malted Barley

2012 ◽  
Vol 550-553 ◽  
pp. 1747-1754
Author(s):  
Ya Li Peng ◽  
Fei Hu
Keyword(s):  
Metal Ion ◽  
Ph Value ◽  
Maximum Activity ◽  
Effect Of Temperature ◽  
Purification And Characterization ◽  
Crude Extracts ◽  
Extraction And Purification ◽  
Sds Page ◽  
Limit Dextrinase

Limit dextrinase is one of three main amylases in malted barley, which plays a significant role during the mashing stage of brewing. Due to very low content and similar properties compared to other amylases in malted barley, limit dextrinase is hard to separate effectively. Our work had been directed towards the extraction and purification of limit dextrinase from malted barley. Final products were obtained through fraction precipitation with ammonium sulfate and column chromatography, and purified limit dextrinase acquired a high purity of 31.23 times as much as that of crude extracts. The previous results were also confirmed by sodiumdodecyl sulphate poly-acrylamide gel electrophoresis (SDS-PAGE) revealing a single band of protein (~97KDa). Effect of temperature, pH value, and metal ion on hydrolysis characterization of limit dextrinase was investigated. The results indicated that the maximum activity of purified samples changed significantly compared with that of crude extracts. The activity of purified limit dextrinase could be activated by lower concentration of Mg2+、Ca2+、Mn2+ and inhibited by the action of Zn2+、Fe2+. But this influence was not so obvious for K+.

Partial purification and characterization of an extracellular proteinase from Aeromonas hydrophila strain A4

1988 ◽  
Vol 55 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Efstathios Alichanidis
Keyword(s):  
Aeromonas Hydrophila ◽  
Deae Cellulose ◽  
Enzymic Activity ◽  
Partial Purification ◽  
Significant Activity ◽  
Metal Chelators ◽  
Purification And Characterization ◽  
Tris Maleate ◽  
Ph Range

SummaryAn extracellular metalloproteinase from Aeromonas hydrophila strain A4, isolated from milk, was purified by a factor of 300 by chromatogrpahy on DEAE-cellulose and Sephadex G-150. The enzyme had a mol. wt of 43000 and contained 2 g atom Ca/mol. It was active over a pH range 4·8–9·5 and had optimum activity on casein at pH 7·0 with Km = 0·17 mM. It was strongly inactivated by metal chelators and the apoenzyme was fully reactivated with Ca2+, Mn2+ or Co2+. Heavy metal ions such as Ag+, Hg2+, Fe2+, Zn2+, Cd2+, Ni2+ and Cu2+ totally or partly inactivated the enzymic activity at 5 mM concentration. The enzyme was not inactivated by diisopropylfluorophosphate, soyabean trypsin inhibitor or sulphydryl group reagents. It was optimally active at 45 °C; above 50 °C activity declined rapidly, but significant activity persisted at 4 °C. It was heat labile in phosphate or Tris-maleate buffer but exogenous Ca2+ afforded protection.

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