Glutamine synthetase from an alkalophilic
Bacillus No. 170 was purified to homogeneity from cells grown in synthetic medium at pH 9.0. The purified enzyme had a molecular weight of 600, 000 and a subunit size of 50, 000, similar to the enzymes from
Bacillus subtilis and
Bacillus cereus. Either Mg
2+ or Mn
2+ activated the enzyme; however, the highest activity was obtained when 20mM Mg
2+ with 0.2mM Mn
2+ were added to the assay mixture. The peculiar divalent cation dependency of the glutamine synthetase was similar to that of other
Bacillus enzymes but differed from that of the enteric bacteria enzymes. The kinetic properties of the enzyme, such as optimum pH,
Km for each substrate,
Vmax values, and inhibition by glutamine, were similar to those in the case of other
Bacillus enzymes. The enzyme from this alkalophilic
Bacillus was modified by iodoacetoamide or the ATP analog, 5′-
p-fluorosulfonyl benzoyladenosine (FSBA). Only Mg
2+-dependent activity was decreased by iodoacetamide, whereas each of the Mn
2+-, Mg
2+-, and Mg
2+ plus Mn
2+-dependent activities was decreased with FSBA. The sequence of the NH
2-terminal 20 amino acids of alkalophilic
Bacillus glutamine synthetase was similar to those of other
Bacillus enzymes.
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