Ac-PAL-AMC is a fluorogenic substrate for the β1i LMP2 subunit of the 20S immunoproteasome. Upon cleavage, 7-amino-4-methylcoumarin (AMC) is released and its fluorescence can be used to quantify the activity of the β1i LMP2 subunit of the 20S immunoproteasome. Ac-PAL-AMC is selective for the immunoproteasome over the constitutive proteasome. AMC displays excitation emission maxima of 351 430 nm, respectively.