Kinetics of metabolic pathways. Transient response of the glycolytic system after phosphofructokinase reaction to ADP input.

1. Transient response of the glycolytic system, after phosphofructokinase reaction, to ADP input was studied in a metabolic model in vitro, obtained from rat muscle. 2. Under ADP addition to the system, NADH concentration is largely enhanced to be decreased later, showing a very characteristic pulse whose parameters can be used to describe some features of the transition state. 3. NADH pulse was repeatedly obtained by means of successive ADP inputs to the system. 4. The effect of different variables on NADH pulse was studied, these results suggesting a possible role for different steps on this response. 5. The possible relation between the pulse of NADH and oscillatory behaviour of glycolysis is discussed.