Kinetic and thermodynamic parameters for oxygen binding to the allosteric states of Panulirus interruptus hemocyanin |
| |
Authors: | Antonini E Brunori M Colosimo A Kuiper H A Zolla L |
| |
Affiliation: | Institute of Chemistry and CNR Centre for Molecular Biology, and Department of Biochemistry, Faculty of Medicine, II University of Rome, 00185 Rome, Italy. |
| |
Abstract: | The temperature dependence of the oxygen binding equilibria and kinetics of Panulirus interruptus hemocyanin has been analyzed within the context of the two-state allosteric model. Oxygenation of the T-state is characterized by a more negative value of DeltaH than that of the R-state; therefore, cooperative effects in oxygen binding to P. interruptus hemocyanin are thermodynamically governed by favorable entropy changes. The allosteric transition in the unliganded derivative shows an enthalpy-entropy compensation effect. The activation enthalpies for oxygenation and deoxygenation of the T-state are larger than those for the R-state, while the activation entropies are favorable for the T-state and unfavorable for the R-state. Thus, the activation free energies for oxygen binding to the T- and R-states are similar, while for the deoxygenation reaction DeltaG++ is smaller for the T-state. The analysis reported confirms the applicability of the Monod-Wyman-Changeux two-state allosteric model to P. interruptus hemocyanin and yields a complete thermodynamic characterization of oxygen binding under both equilibrium and dynamic regimes. |
| |
Keywords: | Linear energy converter Flux response coefficient Coupling degree Force ratio Parameter isomorphism |
本文献已被 ScienceDirect PubMed 等数据库收录! |