Figure 3.

Pre-steady-state reactivity of the fully reduced ascorbate-free PHM. (a) Time evolution of the product in the absence of excess ascorbate, k_obs = 150 s^–1: blue trace represents the consumption of dansyl-YVG substrate and orange trace is the rate of generation of the dansyl-α-hydroxyglycine-YVG product. (b) Time evolution of substrate consumption (blue) and product generation (orange) in the presence of excess ascorbate (6 mM), k_obs = 36 s^–1. (c) Bar graph showing an increase in the mole fraction of product per mole of enzyme as a function of added ascorbate. (d) Ascorbate dependence of product formation fitted to a ligand-binding event with K_D = 117 μM.