J. Biochem, 1982, Vol. 91, No. 1 283-289
© 1982 Japanese Biochemical Society
research-article |
D-Glucosaminate Dehydratase from Agrobacterium radiobacter. Physicochemical and Enzymological Properties
*Department of Chemistry, Faculty of Science, Nara Women's University Nara, Nara 630
**Laboratory of Microbial Biochemistry, Institute for Chemical Research, Kyoto University Uji, Kyoto 611
The bacterial distribution of D-glucosaminate dehydratase EEC 4.2.1.26 [EC] ] was investigated and Agrobacterium radiobacter (IAM 1526) was found to have the highest enzyme activity. The enzyme was formed inducibly in a glycerol-urea medium by D-glucosaminate, D-galactosamine, and D-glucosamine, but not by D-mannosamine. The enzyme purified from the cells grown in the glucosamine-glycerol-urea medium was shown to be homogeneous by ultracentrifugation. The molecular weight was determined to be about 66,000 by the sedimentation equilibrium method, and 72,800 by the gel permeation chromatography low-angle light scattering method. The pH optimum is 8.39.0. The enzyme catalyzed the dehydration of D-glucosaminate (relative activity: 100, Km: 2.8 mM), D-galactosaminate (31.5, 5.0 mM), D-manno saminate (17.5, 29 mM), D-threonifle (5.1, 4.8 mM), D-serine (3.2, 0.026 mM), and L-serine (1.1, ND), but not L-threonine. The reverse reaction does not occur. The enzyme is inhibited by typical inhibitors of pyridoxal 5'-phosphate enzymes, such as L-penicillamine, and also by carbonyl reagents, thiol reagents, divalent metals, and several D-amino acids and D-amino sugars.