Partial and complete alteration of surface charges of carboxymethylcellulase by chemical modification: thermostabilization in water-miscible organic solvent

Siddiqui, Khawar Sohail; Shemsi, Ahsan M.; Anwar, Munir A.; Rashid, Muhammad Hamid; Rajoka, Muhammad Ibrahim

doi:10.1016/s0141-0229(98)00170-7

Cited by 51 publications

(31 citation statements)

References 32 publications

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“…Aliquots were withdrawn at different times, cooled in ice for 3 h (Violet and Meunier 1989), and assayed for enzyme activity. The data were fitted to the first order plots and analysed as described earlier (Siddiqui et al 1999). The thermodynamic parameters for thermostability were calculated by rearranging the Eyring absolute rate equation as described by Eyring and Stearn (1939) and Rashid and Siddiqui 1998).…”

Section: Thermodynamics Of Enzyme Stabilitymentioning

confidence: 99%

Purification and characterization of xylanases from Thermomyces lanuginosus and its mutant derivative possessing novel kinetic and thermodynamic properties

Bokhari

Latif

Rajoka

2008

World J Microbiol Biotechnol

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Xylanases produced from a locally isolated strain of Thermomyces lanuginosus and its mutant derivative were purified to a yield of 39.1 and 42.83% with specific activities of 15,501 and 17,778 IU mg -1 protein, respectively. The purification consisted of two steps i.e., ammonium sulphate precipitation, and gel filtration chromatography. The mutant enzyme showed high affinity for substrate, with a K m of 0.098 mg ml -1 as compared to wild type enzyme showing K m of not less than 0.112 mg ml -1 . It was found that pH values of 8.1 and 7.3 were best for activity of the mutant and wild-type-derived enzymes, respectively. The values of pK a of the acidic limbs of both enzymes were the same (5.0 and 4.9, respectively) but the pK a value of the basic limb was slightly increased, indicating the participation of a carboxyl group present in a non-polar environment. Temperatures of 70 and 65°C were found optimal for mutant and wild-derived xylanase, respectively. Enzymes displayed a high thermostability showing a half life of 31.79 and 6.0 min (5.3-fold improvement), enthalpy of denaturation (DH*) of 146.06 and 166.95 kJ mol -1 , entropy of denaturation (DS*) of 101.44 and 174.67, and free energy of denaturation (DG*) of 110.25 and 105.29 kJ mol -1 for mutant-and wildorganism derived enzyme, respectively at 80°C. Studies on the folding and stability of cellulase-less xylanases are important, since their biotechnological employments require them to function under extreme conditions of pH and temperature. The kinetic and thermodynamic properties suggested that the xylanase from the mutant organism is better as compared to xylanase produced from the wild type and previously reported strains of same species, and may have a potential usage in various industrial fields.

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Section: Thermodynamics Of Enzyme Stabilitymentioning

confidence: 99%

Purification and characterization of xylanases from Thermomyces lanuginosus and its mutant derivative possessing novel kinetic and thermodynamic properties

Bokhari

Latif

Rajoka

2008

World J Microbiol Biotechnol

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“…Further insight into the nature of these changes can be obtained from the use of activation parameters to analyze structure-activity relationships of biocatalysts (Jensen et al, 1997;Siddiqui et al, 1999). Table V shows a decrease in activation enthalpy with DMSO at each temperature investigated.…”

Section: Discussionmentioning

confidence: 99%

“…Thermodynamic activation parameters were calculated based on the Eyring absolute rate equation (Eyring and Stearn, 1939;Lonhienne et al, 2000;Siddiqui et al, 1999):…”

Section: Calculation Of Activation Parametersmentioning

confidence: 99%

Structural and catalytic response to temperature and cosolvents of carboxylesterase EST1 from the extremely thermoacidophilic archaeon Sulfolobus solfataricus P1

Sehgal

Tompson

Cavanagh

et al. 2002

Biotech & Bioengineering

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The interactive effects of temperature and cosolvents on the kinetic and structural features of a carboxylesterase from the extremely thermoacidophilic archaeon Sulfolobus solfataricus P1 (Sso EST1) were examined. While dimethylformamide, acetonitrile, and dioxane were all found to be deleterious to enzyme function, dimethyl sulfoxide (DMSO) activated Sso EST1 to various extents. This was particularly true at 3.5% (v/v) DMSO, where k(cat) was 20-30% higher than at 1.2% DMSO, over the temperature range of 50-85 degrees C. DMSO compensated for thermal activation in some cases; for example, k(cat) at 60 degrees C in 3.5% DMSO was comparable to k(cat) at 85 degrees C in 1.2% DMSO. The relationship between DMSO activation and enzyme structural characteristics was also investigated. Nuclear magnetic resonance spectroscopy and circular dichroism showed no gross change in enzyme conformation with 3.5% DMSO between 50 and 80 degrees C. However, low levels of DMSO were shown to have a small yet significant change in enzyme conformation. This was evident through the reduction of Sso EST1's melting temperature and changes in the microenvironment of the enzyme's tyrosine and tryptophan residues at 3.5% versus 1.2% (v/v) solvent. Finally, activation parameter analysis based on kinetic data, at 1.2% and 3.5% DMSO, implied an increase in conformational flexibility with additional cosolvent. These results suggest the activating effect of DMSO was related to small changes in the enzyme's structure resulting in an increase in its conformational flexibility. Thus, in addition to their use for solubilizing hydrophobic substrates in water, cosolvents may also serve as activators in applications involving thermostable biocatalysts at sub-optimal temperatures.

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“…The thermodynamics of the irreversible thermoinactivation of inulinase was determined by rearranging the Eyring's absolute rate equation, derived from the transition state theory [6],…”

Section: Theoreticalmentioning

confidence: 99%

Kinetic and thermodynamic characterizations of thermal inactivation of the inulinase produced by Kluyveromyces latics

Zhao¹,

Zhao²,

Wang³

2016

Proceedings of the 2016 5th International Conference on Advanced Materials and Computer Science

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Abstract. The present study evaluated the kinetics and thermodynamic parameters for the thermal inactivation of inulinase. The thermoinactivation behaviours of inulinase under 40, 50, 60 and 70℃ were observed. Residue activity of inulinase after incubated for a certain time under the tested temperatures, respectively. The inactivation rate constants (k in ) of inulinase under different temperatures were calculated and used to estimate the activation energy for irreversible inactivation E a(in) of inulinase, which was 236.9 kJ mol -1 .

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Partial and complete alteration of surface charges of carboxymethylcellulase by chemical modification: thermostabilization in water-miscible organic solvent

Cited by 51 publications

References 32 publications

Purification and characterization of xylanases from Thermomyces lanuginosus and its mutant derivative possessing novel kinetic and thermodynamic properties

Purification and characterization of xylanases from Thermomyces lanuginosus and its mutant derivative possessing novel kinetic and thermodynamic properties

Structural and catalytic response to temperature and cosolvents of carboxylesterase EST1 from the extremely thermoacidophilic archaeon Sulfolobus solfataricus P1

Kinetic and thermodynamic characterizations of thermal inactivation of the inulinase produced by Kluyveromyces latics

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