Spectral properties and reactivity towards azide of Dicrocoelium dendriticum met-hemoglobin
| Autor: | Jan Derk G. Smit, Gm Giacometti, Paolo Ascenzi, G.A. Gilbert, Kaspar H. Winterhalter, Maurizio Brunori |
|---|---|
| Rok vydání: | 1983 |
| Předmět: |
Azides
Hemeprotein Analytical chemistry Spin transition chemistry.chemical_compound Reaction rate constant Structural Biology medicine Animals Reactivity (chemistry) Dicrocoelium Molecular Biology Methemoglobin biology Chemistry Dicrocoelium dendriticum Hydrogen-Ion Concentration biology.organism_classification Kinetics Models Chemical Spectrophotometry Temperature jump Ferric Azide Protein Binding medicine.drug |
| Zdroj: | Journal of Molecular Biology. 168:181-191 |
| ISSN: | 0022-2836 |
| DOI: | 10.1016/s0022-2836(83)80329-5 |
| Popis: | The spectroscopic properties of Dicrocoelium dendriticum met-hemoglobin, investigated between pH 3·8 and 10·5, display two proton-induced transitions with apparent p K values of 8·1 and 4·7. The spectral changes, over the pH region 6·5 to 10·5, correspond to the high to low spin transition usually observed in ferric hemoproteins. The relaxation time (τ=3·2 ms at the p K ) associated with this transition is closely similar to that observed in Aplysia limacina met-myoglobin, but approximately 1000-fold slower than that of sperm whale met-myoglobin. The spectral changes associated with the more acid transition are in the opposite direction and have not been resolved by the temperature jump method. The rate constants for the reaction of azide with Dicrocoelium dendriticum met-hemoglobin were measured between pH 3·8 and 6·7 by the temperature jump method. Two kinetic schemes, both consistent with the pH dependence of the apparent rate constant for binding of azide, were identified. No objective way of discriminating between the two models is available. However, one of them is amenable to a physical interpretation based on a comparison with the structural, kinetic and spectral properties of other monomeric hemoproteins. |
| Databáze: | OpenAIRE |
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