Model validation in terms of transient response and robustness. (A) Transient responses for the ratio of glutamine to 2-ketoglutarate (N/C ratio) (—) and the active GS concentration (.....) in the cells lacking the GS synthesis control module (the regulation with the GS activity control module alone). The active GS indicates nonadenylylated GS that catalyzes the conversion from glutamate and ammonia to glutamine. The ammonia concentration was decreased to one-fifth at 500 min. The GS activity module was obtained by setting the kinetic parameters K[15,16], which are the association constant between PII or GlnK and NRII, as zero in the full model. (B) Transient responses of the ratio of glutamine to 2-ketoglutarate (N/C ratio) (—) and the active GS concentration (.....) in the full model that consists of the GS activity control and GS synthesis control modules. The ammonia concentration was decreased to one-fifth at 500 min.
