| Autor: |
Simona Horsa, Xiaotang Wang, Jaroslava Miksovska |
| Rok vydání: |
2010 |
| Předmět: |
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| Zdroj: |
Biophysical Journal. 98(3) |
| ISSN: |
0006-3495 |
| DOI: |
10.1016/j.bpj.2009.12.3523 |
| Popis: |
Chloroperoxidase (CPO) is the most versatile heme containing enzyme that exhibits peroxidase, catalase, halogenase and monooxigenase activities. The heme iron coordination resembles to P450s enzymes whereas the composition of the distal pocket is more polar, containing Glu183 hydrogen bounded to His 105 and the heme pocket is connected with the surrounding solvent by two hydrophobic channels. To investigate the ligand-protein interactions in CPO we have employed time-resolved photoacoustic calorimetry and transient absorption study. Unlike other peroxidases, the CO photo-dissociation from CPO can be described as a two step process with distinct volume and enthalpy changes. The photodissociation of Fe-CO bond is associated with negligible volume change (V = 1 ± 8 mL mol−1 ) and a positive enthalpy change (H = 48 ± 34 kcal mol−1). Subsequent CO escape from the protein matrix is characterized by a positive volume change (25 ± 8 mL mol−1) and insignificant enthalpy change (−2 ± 33 kcal mol−1) and occurs with a lifetime of ∼ 20 ns. Similar thermodynamic parameters were found in D2O at pD 4.6 but the CO photo-release occurs two times slower (∼ 50 ns) than in phosphate buffer. Presence of substrates (halides or cyclopentanedione) did not show a significant impact on the thermodynamic profiles associated with the ligand dissociation. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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