Kinetic parameter assumptions
in vitro values represent the in vivo parameters
- protein concentration in vitro much lower than in vivo
- enzyme interactions (enzymes, cytoskeleton, membrane, …)
- samples used to measure kinetics may contain unknown conc. of effectors (i.e. fructose 2,6-bisphosphate)
- enzyme catalyzed enzyme modifications
all possible concentrations of interacting molecules been considered (interpolating)
- e.g. glutamine synthase (unusually large # of known effectors)
- 3 substrates, 3 products, 9 significant effectors
- 415 (~109) measurements: 4 different conc. of 15 molecules (Savageau, 1976)
- in vivo probably even more complex, but approximations are effective.
have all interacting molecules been discovered?