Metal ion binding to d -xylose isomerase from Streptomyces violaceoruber
| Autor: | C. K. de Bruyne, R Cornelis, M Callens, Hilda Kersters-Hilderson, P Tomme, W Vangrysperre |
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| Rok vydání: | 1988 |
| Předmět: |
Xylose isomerase
Conformational change Cations Divalent Macromolecular Substances Protein Conformation Stereochemistry Isomerase Binding Competitive Biochemistry Ion Metal Naphthalenesulfonates Magnesium Binding site Molecular Biology Aldose-Ketose Isomerases chemistry.chemical_classification Binding Sites Cobalt Cell Biology Binding constant Streptomyces Crystallography Enzyme chemistry visual_art visual_art.visual_art_medium Calcium Spectrophotometry Ultraviolet Carbohydrate Epimerases Research Article Nitroso Compounds |
| Zdroj: | Biochemical Journal. 250:285-290 |
| ISSN: | 1470-8728 0264-6021 |
| DOI: | 10.1042/bj2500285 |
| Popis: | The binding of two activating cations, Co2+ and Mg2+, and of one inhibitory cation, Ca2+, to D-xylose isomerase from Streptomyces violaceoruber was investigated. Equilibrium-dialysis and spectrometric studies revealed that the enzyme binds 2 mol of Co2+/mol of monomer. Difference absorption spectrometry in the u.v. and visible regions indicated that the environment of the first Co2+ ion is markedly different from that of the second Co2+ ion. The first Co2+ appears to have a six-co-ordinate. The conformational change induced by binding of Co2+ to the first site is maximum after the addition of 1 equivalent of Co2+ and yields a binding constant greater than or equal to 3.3 × 10(6) M-1. Binding of Co2+ to the second, weaker-binding, site caused a visible difference spectrum. The association constant estimated from Co2+ titrations at 585 nm agrees satisfactorily with the value of 4 × 10(4) M-1 obtained from equilibrium dialysis. Similarly, the enzyme undergoes a conformational change on binding of Mg2+ or Ca2+, the binding constants being estimated as 1 × 10(5) M-1 and 5 × 10(5) M-1 respectively. Competition between the activating Mg2+ and Co2+ and the inhibitory Ca2+ ion for both sites was further evidenced by equilibrium dialysis and by spectral displacement studies. |
| Databáze: | OpenAIRE |
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