TAILIEUCHUNG - Báo cáo khoa học: Influence of divalent cations on the structural thermostability and thermal inactivation kinetics of class II xylose isomerases

The effects of divalent metal cations on structural thermostability and the inactivation kinetics of homologous class II d-xylose isomerases (XI; EC ) from mesophilic (Escherichia coliand Bacillus licheniformis), thermophilic (Thermoanaerobacterium thermosulfurigenes), and hyperther-mophilic (Thermotoga neapolitana) bacteria were examined. | iFEBS Journal Influence of divalent cations on the structural thermostability and thermal inactivation kinetics of class II xylose isomerases Kevin L. Epting1 Claire Vieille2 J. Gregory Zeikus2 and Robert M. Kelly1 1 Department of ChemicalEngineering North Carolina State University Raleigh NC USA 2 Department of Biochemistry and Molecular Biology Michigan State University East Lansing MI USA Keywords inactivation kinetics metal cofactors thermostability xylose isomerases Correspondence R. M. Kelly Department of Chemical Engineering North Carolina State University Raleigh nC 27695-7905 Fax 1 919 515 3465 Tel 1 919 515 6396 E-mail rmkelly@ Received 27 November 2004 accepted 20 January 2005 doi The effects of divalent metal cations on structural thermostability and the inactivation kinetics of homologous class II D-xylose isomerases XI EC from mesophilic Escherichia coli and Bacillus licheniformis thermophilic Thermoanaerobacterium thermosulfurigenes and hyperther-mophilic Thermotoga neapolitana bacteria were examined. Unlike the three less thermophilic XIs that were substantially structurally stabilized in the presence of Co2 or Mn2 and Mg2 to a lesser extent the melting temperature Tm 100 C of T. neapolitana XI TNXI varied little in the presence or absence of a single type of metal. In the presence of any two of these metals TNXI exhibited a second melting transition between 110 C and 114 C. TNXI kinetic inactivation which was non-first order could be modeled as a two-step sequential process. TNXI inactivation in the presence of 5 mM metal at 99-100 C was slowest in the presence of Mn2 half-life t1 2 of 84 min compared to Co2 t1 2 of 14 min and Mg2 t1 2 of 2 min . While adding Co2 to Mg2 increased TNXI s t1 2 at 99-100 C from 2 to min TNXI showed no significant activity at temperatures above the first melting transition. The results reported here suggest that unlike the other class II XIs examined single .

• Báo cáo khoa học
• Report medicine
• traditional medicine
• scientific reports
• genetics
• Structural biochemistry
• Structural Biology
• medical knowledge
• medical research
• analysis of cytoplasmic
• oxidation
• Crystal structure
• bacteria
• hemoglobin
• medicine
• cell proliferation
• breast cancer
• chemical reaction
• gastric cancer
• hormone medicine
• tumor cells
• biochemical studies
• environmental medicine