Vanadate inhibition of ATP and p-nitrophenyl phosphate hydrolysis in the fragmented sarcoplasmic reticulum
| Autor: | Raisa S. Utegalieva, Victor I. Vashchenko, Oleg V. Esyrev |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Biophysics
chemistry.chemical_element Calcium-Transporting ATPases Calcium Biochemistry Nitrophenols chemistry.chemical_compound Adenosine Triphosphate Organophosphorus Compounds Structural Biology ATP hydrolysis Animals Magnesium Vanadate Molecular Biology Magnesium ion Rana ridibunda chemistry.chemical_classification 4-Nitrophenylphosphatase Oxalates Binding Sites Hydrolysis Oxalic Acid Endoplasmic reticulum Phosphate Calcium ATPase Sarcoplasmic Reticulum Enzyme chemistry Vanadates |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 1079:8-14 |
| ISSN: | 0167-4838 |
| DOI: | 10.1016/0167-4838(91)90017-t |
| Popis: | The vanadate inhibition of the Ca(2+)-ATPase activity was analysed both in intact sarcoplasmic reticulum vesicles and in the presence of low concentrations of Tween 20, using ATP and p-nitrophenyl phosphate as substrates. The saturation of the internal low-affinity calcium-binding sites protects the enzyme against vanadate inhibition, because: (1) p-nitrophenyl phosphate hydrolysis is not inhibited by vanadate in intact vesicles, but inhibition developed after solubilization with detergents; (2) the vanadate inhibition of the p-nitrophenyl phosphate hydrolysis in solubilized preparations is prevented by free Ca2+ concentrations higher than 10(-3) M and vanadate competes with calcium (10(-5)-10(-3) M); and (3) the vanadate inhibition of ATP hydrolysis is decreased with an increase in vesicular Ca2+ concentration. The presence of magnesium ions is indispensable for the vanadate effect. The vanadate inhibition is non-competitive with respect to Mg-p-nitrophenyl phosphate and uncompetitive with respect to Mg-ATP. However, in the presence of dimethyl sulfoxide, which facilitates phosphorylation of the enzyme, the inhibition is converted to a competitive one with respect to a substrate. The results suggest, that in the process of enzyme operation vanadate interacts with the unliganded E form of Ca(2+)-ATPase, occupying probably an intermediate position between the E2 and E1 forms, with the formation of an E2 Van complex, that imposes the inhibition on the Ca(2+)-ATPase activity. |
| Databáze: | OpenAIRE |
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