| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1235149 | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2011 | 7 Pages |
The native form of Cu/Zn-superoxide dismutase, isolated from fungal strain Humicola lutea 103 is a homodimer that coordinates one Cu(2+) and one Zn(2+) per monomer. Cu(2+) and Zn(2+) ions play crucial roles in enzyme activity and structural stability, respectively. It was established that HLSOD shows high pH and temperature stability. Thermostability of the glycosylated enzyme Cu/Zn-SOD, isolated from fungal strain H. lutea 103, was determined by CD spectroscopy. Determination of reversibility toward thermal denaturation for HLSOD allowed several thermodynamic parameters to be calculated. In this communication we report the conditions under which reversible denaturation of HLSOD exists. The narrow range over which the system is reversible has been determined using the strongest test of two important thermodynamic independent variables (T and pH). Combining both these variables, the “phase diagram” was determined, as a result of which the real thermodynamic parameters (ΔCp, ΔHexp°, and ΔGexp°) was established. Because very narrow pH-interval of transitions we assume they are as result of overlapping of two simple transitions. It was found that ΔHo is independent from pH with a value of 1.3 kcal/mol and 2.8 kcal/mol for the first and the second transition, respectively. ΔGo was pH-dependent in all studied pH-interval. This means that the transitions are entropically driven, these. Based on this, these processes can be described as hydrophobic rearrangement of the quaternary structure. It was also found that glycosylation does not influence the stability of the enzyme because the carbohydrate chain is exposed on the surface of the molecule.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Reversibility of glycosylated Humicola lutea Cu/Zn-SOD was determined by CD spectroscopy. ► In this communication we report the thermal conditions under which HLSOD exists. ► The narrow range over which the system is reversible (T and pH) was determined. ► The real thermodynamic parameters (ΔCp, ΔHexp°, and ΔGexp°) was established.
