biovision K142-100 Cell and tissue lysates ? Detection method- Fluorescence (Ex/Em 400/505) ? Species reactivity- Mammalian ? Kit size- 100 assays ? Applications- Detects alternative proteolytic enzymes such as the lysosomal cathepsin proteases that can initiate or propagate proapoptotic signals. Cathepsin L Activity Assay Kit: Rapid & Convenient Fluorometric Assay to Measure Cathepsin L Activity within 1-2 hrs. 100 Assays. Apoptosis can be mediated by mechanisms other than the traditional caspase-mediated cleavage cascade. There is growing recognition that alternative proteolytic enzymes such as the lysosomal cathepsin proteases may initiate or propagate proapoptotic signals. Cathepsins are lysosomal enzymes that are also used as sensitive markers in various toxicological investigations. The Cathepsin-L Activity Assay kit is a fluorescence-based assay that utilizes the preferred cathepsin-L substrate sequence FR labeled with AFC (amino-4-trifluoromethyl coumarin). Cell lysates or other samples that contain cathepsin-L will cleave the synthetic substrate FR-AFC to release free AFC.