Theory 07/Thresholds & Tipping/Enzyme kinetics
Cooperativity Has an Onset
The claim
Enzymes show cooperative kinetics only above a threshold in substrate occupancy, so the same enzyme responds hyperbolically at low substrate and sigmoidally at high.
01Mechanism
Cooperativity requires multiple sites to be engaged; below the occupancy where the first binding event shifts the next, the response is indistinguishable from simple binding.
02Prediction
The Hill coefficient should rise above an occupancy threshold.
03Refutation
Cooperativity constant across occupancy would remove the onset.