Abstract
Dual coenzyme-specific glutamate dehydrogenase (GDH) is regulated by extracellular concentrations of ammonia in members of the Bacteroides fragilis group, including B. fragilis, B. ovatus, B. distasonis, and B. vulgatus, as shown previously in B. fragilis (YAMAMOTO et al., J. Gen. Appl. Microbiol., 30, 499 (1984); J. Gen. Microbiol., 133, 2773 (1987)). High specific activities of GDH were observed in extracts prepared from the respective species grown with limited amounts of ammonia, and GDHs were inactivated by adding NH4Cl at high concentrations to cultures growing with limited amounts of ammonia. The values of Km of GDHs from the bacterial species were in ranges of 1-5mM, 0.14-0.7mM, and 0.006-0.02mM for NH4Cl, 2-oxoglutarate, and NADPH, respectively, and the optimum pHs were around 8.0 in the reductive amination. GDH activities in the four species were inhibited to the same extent by an antiserum prepared against the B. fragilis GDH, and immunoprecipitin bands fused with each other without a spur in a double immunodiffusion test. Activities of glutamine synthetase and glutamate synthase were also found but were 1% of the NADPH-activities of GDH in all the bacterial species.
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