Activation of sphingomyelinase from Bacillus cereus by Zn2+ hitherto accepted as a strong inhibitor
| Autor: | Ayumi Yoshida, Hiromi Itoh, Shinobu Fujii, Hiroh Ikezawa, Satoko Higashi, Kiyoshi Ikeda |
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| Rok vydání: | 2005 |
| Předmět: |
Stereochemistry
Metal ions in aqueous solution Inorganic chemistry Biophysics Bacillus cereus Models Biological Biochemistry Catalysis Chlorides Enzyme kinetics Binding site Molecular Biology Ions chemistry.chemical_classification Manganese Binding Sites biology Hydrolysis Substrate (chemistry) Cobalt Hydrogen-Ion Concentration biology.organism_classification Enzyme Activation Kinetics Zinc Sphingomyelin Phosphodiesterase Enzyme Models Chemical chemistry Cereus Zinc Compounds Sphingomyelin Copper Protein Binding |
| Zdroj: | Archives of Biochemistry and Biophysics. 436:227-236 |
| ISSN: | 0003-9861 |
| DOI: | 10.1016/j.abb.2005.02.019 |
| Popis: | Sphingomyelinase (SMase) from Bacillus cereus has been known to be activated by Mg 2+ , Mn 2+ , and Co 2+ , but strongly inhibited by Zn 2+ . In the present study, we investigated the effects of several kinds of metal ions on the catalytic activity of B. cereus SMase, and found that the activity was inhibited by Zn 2+ at its higher concentrations or at higher pH values, but unexpectedly activated at lower Zn 2+ concentrations or at lower pH values. This result indicates that SMase possesses at least two different binding sites for Zn 2+ and that the Zn 2+ binding to the high-affinity site can activate the enzyme, whereas the Zn 2+ binding to the low-affinity site can inactivate it. We also found that the binding of substrate to the enzyme was independent of the Zn 2+ binding to the high-affinity site, but was competitively inhibited by the Zn 2+ binding to the low-affinity site. The binding affinity of the metal ions to the site for activating the enzyme was determined to be in the rank-order of Mg 2+ = Co 2+ 2+ 2+ . It was also demonstrated that these four metal ions competed with each other for the same binding site on the enzyme molecule. |
| Databáze: | OpenAIRE |
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