d-Xylose isomerase from Streptomyces violaceoruber: Structural and catalytic roles of bivalent metal ions

• Published in: Enzyme and microbial technology Vol. 10; no. 11; pp. 695 - 700
• Main Authors: Callens, Mia, Kersters-Hilderson, Hilda, Vangrysperre, Werner, De Bruyne, Clement K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.11.1988; Elsevier Science
• Subjects: absorption spectroscopy; Analytical, structural and metabolic biochemistry; Biological and medical sciences; cobalt(II); d-Xylose isomerase; denaturating conditions; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; gel electrophoresis; Isomerases; magnesium(II); metal(II) effects; Streptomyces violaceoruber; xylose isomerase; d-Xylose isomerase; metal(II) effects; denaturating conditions; Streptomycetaceae; Stability; Gel electrophoresis; Enzyme; Industrial application; Denaturation; Metal ion; Manganese II; Cobalt «II; Actinomycetales; Enzymatic activity; Xylose isomerase; Bacteria; Actinomycetes; Streptomyces violaceoruber; Catalyst; Atomic absorption spectrometry
• ISSN: 0141-0229; 1879-0909
• DOI: 10.1016/0141-0229(88)90064-6

d-Xylose isomerase from Streptomyces violaceoruber has two nonequivalent bivalent metal ion sites. The activity and stability of the enzyme-[M(II),—] and the enzyme-[M(II),M(II)]-complexes under various denaturing conditions have been studied and indicate that (i) denaturation is always accompanied by irreversible dissociation of the tetrameric structure to monomers; (ii) treatment with 0.1% sodium dodecyl sulfate causes reversible dissociation into active dimers; the equilibrium tetramer dimers is unaffected by Co(II) or Mg(II); (iii) addition of 1 eq Co(II) per monomer or binding of Co(II) at the conformational high-affinity site markedly enhances the structural stability of d-xylose isomerase against elevated temperature, urea, guanidinium hydrochloride, ethanol, and acetone; (iv) the stabilizing effect of Mg(II) at the conformational site is less evident; (v) binding of bivalent metal ions at the lower-affinity site is required for initiation of catalytic activity; (vi) the activating effect of Mg(II) is superior to that of Co(II).