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Abstract
A functional role of Co2+ and Mn2+ in the d-glucose- and d-xylose-isomerizing reactions by d-glucose-isomerizing enzyme obtained from the cells of Bacillus coagulans, strain HN–68 was investigated. (1) The enzyme required Co2+ and Mn2+ for d-glucose- and d-xylose-isomerizing activities, respectively. (2) The enzyme which bound the metal, Co2+- or Mn2+-enzyme, was active form. Co2+ was bound to the enzyme in a molar ratio of 4:1. (3) The rate of activation by metal ion varied with incubation pH. (4) The binding of substrate to the enzyme was completely independent in the presence of metal ions. (5) However, it seemed unlikely that the Co2+ and Mn2+ acted as catalyzer on the reaction. (6) The binding sites for Co2+ and Mn2+ were different from each other. (7) The experimental data obtained might be successfully explained in terms of the suitable conformational changes for d-glucose and d-xylose isomerization, which were induced in the catalytic sites of the enzyme by binding Co2+ and Mn2+, respectively.