The FRET substrate Mca-RPKPYA-Nva-WMK(Dnp)-amide was hydrolyzed 60 times more rapidly by stromelysin 1 (MMP-3) (kcat/Km= 59400 M⁻¹s⁻¹) than by interstitial collagenase (MMP-1). However, it showed little discrimination between MMP-3, gelatinase A (MMP-2) (kcat/Km= 54000 M⁻¹s⁻¹), and gelatinase B (MMP-9) (kcat/Km= 55300 M⁻¹s⁻¹). Metalloelastase (MMP-12) digested this fluorogenic substrate with a kcat/Km of 243000 M⁻¹s⁻¹. For a fluorescent standard see M-2250.