| Abstract |
Streptomyces albus T-12 which had been isolated and identified in the laboratory, was selected for the studies on the cultural conditions on the production of D-xylose isomerase and the enzymological characteristics using the partially purified enzyme. The best results in the enzyme production came from D-xylose medium than wheat bran. The divalent metal ions as Co^2+, Fe^2+, Zn^2+ and Cu^2+ retard or inhibit the cell-growth at the early stages of mycelia propagations, and T-12 strain is especially sensitive to Co^2+. After 60 hours of shaking cultivation at 30℃ and 200 rpm, a maximum enzyme activitz, 0.49 enzyme units, was obtained. Cell-free enzyme obtained from mycelia heat-treated in the prescence of 0.5mM Co^2+, showed a 2.4-fold increase in specific than the enzyme from untreated mycelia. The specific activity of the purified enzyme through Sephadex G-150 columm showed 180 fold to the crude enzyme. The effective activators of the enzyme appeared to be Mg^2+ and Co^2+ ions, and it exhibited the maximal enzyme activity showed at pH 7.0 and at temperature around 80℃ when Mg^2+ and Co^2+ ions were added. The enzyme isomerized D-glucose, D-xylose, D-ribose, L-arabinose, D-mannose, and L-rhamnose in the present of Mg^2+ and Co^2+ ions as an activatiors. Mg^2+ and Co^2+ ions were non-competitively bound at different allosterix sites of enzyme molecule. Mg^2+(5mM) or Co^2+(1.0mM) protected against the thermal denaturations of the enzyme activities. The michaelis constant (Km) and V_max values of the emzyme for D-glucose and D-xylose were 0.52M, 2.12 umoles/ml·min. and 0.28M, 0.65 moles/ml·min, respectively. |
