PURIFICATION CRYSTALLIZATION AND PROPERTIES OF D-XYLOSE ISOMERASE FROM LACTOBACILLUS BREVIS

1. 1.d-Xylose isomerase (d-xylose ketol-isomerase, EC 5.3.1.5) has been purified and crystallized from the extracts of d-xylose-grown cells of Lactobacillus brevis 2. 2.The crystalline enzyme appears from its sedimentation pattern to be homogeneous. d-Lyxose is inert with respect to this enzyme. In the reverse reaction, xylose is the only product of d-xylulose, but d-lyxose is not detected in the reaction products of d-xylulose. 3. 3.This enzyme catalyzes the isomerization of d-xylose, d-glucose and d-ribose. The optimum pH is identical for these substrates, 6.0-7.0, while the Michaelis constants are very different: 5·10-3 M for d-xylose, 0.92 M for d-glucose and 0.67 M for d-ribose. 4. 4.This enzyme required manganese ions for its activity and the Michaelis constant was found to be 6.1·10-6 M. © 1968.