Inactivation of aspartic transcarbamylase in sporulating XXXX : demonstration of a requirement for metabolic energy.

@entity26 @entity6883 @entity2861 @entity6626 @entity12742 @entity5537 @entity3881
The aspartic transcarbamylase (ATCase) activity of @entity3881 cells disappears rapidly from stationary-phase cells prior to sporulation. ATCase activity does not appear in the culture fluid during the stationary phase; hence the enzyme appears to be inactivated in the cells. The enzyme is inactivated normally in two different mutants lacking proteases; the activity is very stable in crude extracts of cells or in the culture fluid. These results suggest that ATCase is not inactivated by the general proteolysis that occurs in sporulating bacteria. The inactivation of ATCase can be completely inhibited after it has begun by @entity26 starvation or addition of @entity2861 . Inhibitors of oxidative phosphorylation and electron transport also interrupt the inactivation of ATCase. The inactivation of ATCase is very slow in two mutant strains that are deficient in enzymes of @entity6626 cycle. Addition of @entity12742 to stationary cultures of the mutant strains, which is known to restore depleted @entity6883 pools in these bacteria, also restores inactivation of ATCase. These experiments support the conclusion that the generation of metabolic energy is necessary for the inactivation of ATCase in stationary cells. ATCase activity is stable in growing cells in which ATCase synthesis is repressed by addition of @entity5537 ; the enzyme is inactivated normally, however, when such cells cease growing.
