Fig. 3.

Spectral changes during displacement by DHN of DOPA (a) or dopamine (b and c) from unphosphorylated (a and b) and phosphorylated (c) hTyrH4. Enzyme (30 μM) was incubated with 60 μM L-DOPA or dopamine for 15 min in 10% glycerol, 100 mM KCl, 0.2 mM DTPA, 50 mM HEPES, pH 7, at 10°C, before the spectra indicated by solid lines were taken. DHN was then added to give a final concentration of 1 mM; the spectra indicated by dashed lines were taken after 2.8 h (a) or 12.5 h (b and c).