Figure 5: KI-induced release of the cofactor from PMP-GSAM. (a) Fluorescence emission spectra upon excitation at 330 nm of 2 μM PMP-GSAM in the absence (solid line) and in the presence (dashed line) of 50 mM KI (after 195 minutes incubation). The emission spectra of 2 μM PMP in Tricine (dashed-dotted line) and 1 μM PMP in tricine plus 1 μM PMP-GSAM (dotted line) are shown for comparison. Inset: time course of the fluorescence emission intensity of 2 μM PMP-GSAM ( nm, nm) after the addition of 50 mM KI. (b) Absorbance spectrum of a solution of PMP-GSAM before (solid line) and after (dashed line) treatment with 50 mM KI. The protein solution was mixed with a concentrated solution of KI to a final concentration of 50 mM and extensively dialyzed first against 50 mM KI in tricine buffer pH 7.9 and then against KI-free buffer.