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The Thermal Stability of the Fusarium solani pisi Cutinase as a Function of pH.

Petersen SB, Fojan P, Petersen EI, Petersen MT - J. Biomed. Biotechnol. (2001)

Bottom Line: The ratio between the calorimetric enthalpy (DeltaH(cal)) and the van't Hoff enthalpy (DeltaH(v)) obtained, is far from unity, indicating that cutinase does not exhibit a simple two state unfolding behaviour.The role of pH on the electrostatic contribution to the thermal stability was assessed using TITRA.We propose a molecular interpretation for the pH-variation in enzymatic activity.

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ABSTRACT
We have investigated the thermal stability of the Fusarium solani pisi cutinase as a function of pH, in the range from pH 2-12. Its highest enzymatic activity coincides with the pH-range at which it displays its highest thermal stability. The unfolding of the enzyme as a function of pH was investigated by microcalorimetry. The ratio between the calorimetric enthalpy (DeltaH(cal)) and the van't Hoff enthalpy (DeltaH(v)) obtained, is far from unity, indicating that cutinase does not exhibit a simple two state unfolding behaviour. The role of pH on the electrostatic contribution to the thermal stability was assessed using TITRA. We propose a molecular interpretation for the pH-variation in enzymatic activity.

No MeSH data available.


Salt bridges on the surface of cutinase. Amino acids involved in the formation of salt bridges on the surface of cutinase, as predicted by the pKa shifts using the program TITRA.
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Figure 7: Salt bridges on the surface of cutinase. Amino acids involved in the formation of salt bridges on the surface of cutinase, as predicted by the pKa shifts using the program TITRA.

Mentions: The influence of pH on the titration state of the titratable residues of cutinase was investigated using TITRA [12, 13]. TITRA is based on the modified Tanford Kirkwood model and the Tanford Roxby iterative model for the calculation of the apparent pKa values of solvent accessible residues. It also takes the ionic strength of the solution into account. We mapped the Delphi grid, as described in Materials and Methods on the surface of cutinase at pH 4.0, 6.0, 8.5, and 10.0 (Figure 6). Along the surface of the molecule a network of hydrogen bonds and also salt bridges (Figure 7), provides a possible explanation for the rise of Tm found around pH 6.0.


The Thermal Stability of the Fusarium solani pisi Cutinase as a Function of pH.

Petersen SB, Fojan P, Petersen EI, Petersen MT - J. Biomed. Biotechnol. (2001)

Salt bridges on the surface of cutinase. Amino acids involved in the formation of salt bridges on the surface of cutinase, as predicted by the pKa shifts using the program TITRA.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC113781&req=5

Figure 7: Salt bridges on the surface of cutinase. Amino acids involved in the formation of salt bridges on the surface of cutinase, as predicted by the pKa shifts using the program TITRA.
Mentions: The influence of pH on the titration state of the titratable residues of cutinase was investigated using TITRA [12, 13]. TITRA is based on the modified Tanford Kirkwood model and the Tanford Roxby iterative model for the calculation of the apparent pKa values of solvent accessible residues. It also takes the ionic strength of the solution into account. We mapped the Delphi grid, as described in Materials and Methods on the surface of cutinase at pH 4.0, 6.0, 8.5, and 10.0 (Figure 6). Along the surface of the molecule a network of hydrogen bonds and also salt bridges (Figure 7), provides a possible explanation for the rise of Tm found around pH 6.0.

Bottom Line: The ratio between the calorimetric enthalpy (DeltaH(cal)) and the van't Hoff enthalpy (DeltaH(v)) obtained, is far from unity, indicating that cutinase does not exhibit a simple two state unfolding behaviour.The role of pH on the electrostatic contribution to the thermal stability was assessed using TITRA.We propose a molecular interpretation for the pH-variation in enzymatic activity.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
We have investigated the thermal stability of the Fusarium solani pisi cutinase as a function of pH, in the range from pH 2-12. Its highest enzymatic activity coincides with the pH-range at which it displays its highest thermal stability. The unfolding of the enzyme as a function of pH was investigated by microcalorimetry. The ratio between the calorimetric enthalpy (DeltaH(cal)) and the van't Hoff enthalpy (DeltaH(v)) obtained, is far from unity, indicating that cutinase does not exhibit a simple two state unfolding behaviour. The role of pH on the electrostatic contribution to the thermal stability was assessed using TITRA. We propose a molecular interpretation for the pH-variation in enzymatic activity.

No MeSH data available.