TABLE 4.
Enzyme | Glutamine synthetase-specific activity |
||
---|---|---|---|
Forward reaction (biosynthetic) |
Reverse reaction (transferase)a | ||
Mg2+-dependenta | Mn2+-dependenta | ||
WT | 0.406 ± 0.035 | 0.187 ± 0.009 | 9.555 ± 0.490 |
WT (treated)b | 0.413 ± 0.019 | 0.193 ± 0.012 | 9.643 ± 0.422 |
GS(E304A/A305G) | 0.003 ± 0.001 | 0.005 ± 0.004 | 0.029 ± 0.007 |
GS(E304A/A305G) (treated)b | 0.003 ± 0.001 | 0.005 ± 0.002 | 0.038 ± 0.014 |
WT-E304A/A305G mixed complex | 0.005 ± 0.001 | 0.006 ± 0.004 | 0.037 ± 0.012 |
a 1 unit of GS activity corresponds to the ATP/ADP-dependent formation of 1 nmol of γ-glutamylhydroxamate min−1.
b Samples were treated with 2 m urea then dialyzed to remove urea (see “Experimental Procedures”).