Description
Description: Detect changes in intracellular chymotrypsin-like serine protease enzyme activity in whole living cells with the FLISP, Fluorescent-Labeled Inhibitors of Serine Proteases, product line of assay kits. This assay utilizes a leucine (L) chymotrypsin-targeting amino acid residue linked on the amino terminus with either a carboxyfluorescein (FAM) fluorescent reporter tag. The carboxyl end of the F or L amino acid residue contains a reactive group that targets the catalytic site of serine proteases, consisting of an aminoalkyl phosphonate diphenyl ester (DAP) reactive group. After quickly penetrating the lipid bilayer membranes of the target cell population, the chymotrypsin-targeting FLISP probe will interact with the active catalytic sites of chymotrypsin-like proteases, quickly forming covalent bonds with the reactive serine OH group (when DAP-containing FLISP probes are utilized). In either case, unbound FLISP reagent is easily removed during the wash step, leaving cells with greater quantities of active chymotrypsin-like enzyme activity with a greater fluorescence potential than cells that did not undergo an upregulation of serine protease activity. FLISP probes bearing FAM reporter dyes are excited at 488 nm and emit in the green wavelength range of 525 nm. The red fluorescence FLISP probes that utilize sulforhodamine 101 as the reporter dye are excited at 590 nm and emit at 620 nm. FLISP probes are cell permeant and non-cytotoxic at the concentrations suggested in the assay protocol. The FAM-L-DAP chymotrypsin enzyme detection assay kits can be used in conjunction with your existing apoptosis detection protocols. They have been used successfully in tandem with the red SR FLICA apoptosis detection assay kits to show a parallel upregulation of chymotrypsin-like enzyme activity and caspase activation. Each kit includes either 25 tests or 100 tests of FAM-L-DAP reagent, 10X wash buffer for removing excess FLISP probe following the FLISP incubation step, 10X fixative to stabilize cells if needed for next day analysis, PI vital stain for necrotic cell detection, and Hoechst 33342 dye to stain apoptotic nuclei. FAM-L-DAP stained cells can be analyzed using flow cytometry, fluorescence microscopy, and fluorescence plate reader evaluation methodology.
Background: Chymotrypsin-like enzymes cleave their substrate proteins at the carboxy terminus of amino acids containing hydrophobic aliphatic or aromatic R-group side chains such as those found on leucine and phenylalanine amino acid structures [1]. Compared to our FAM-F-DAP FLISP probe, the FAM-L-DAP FLISP probe contains a leucine amino acid rather than a phenylalanine in the P1 position. Because both leucine and phenylalanine contain a hydrophobic R-group side chain structure, they could both represent a type of fluorescent- labeled analog of the early chymotrypsin-like enzyme inhibitor N-tosyl- L-phenylalanine chloromethyl ketone (TPCK) [2]. Early studies using topoisomerase inhibitors in HL-60 cells indicated that TPCK, N-tosyl-L-lysine chloromethyl ketone (TLCK) and other serine protease inhibitors were able to prevent internucleosomal DNA degradation associated with apoptosis [3]. Dual staining experiments have used our original green FLISP chymotrypsin detection probe (FAM-F-CMK) and red FLICA poly caspase detection probe in the presence or absence of z-VAD-FMK, TPCK, or TLCK caspase or serine protease inhibitors with published success [2,4]. alpha-Aminoalkyl phosphonates were developed to address the need for reagents capable of covalently labeling the reactive serine-OH amino acid groups within the catalytic sites of serine proteases [5-6]. Chloromethyl ketone-based inhibitors very efficiently perform the task of labeling serine proteases but also have the capability of reacting with other enzymes and proteins in a non-specific manner and are more subject to hydrolysis over time in aqueous/cell culture media environments [7]. FLISP probes, containing this peptidyl ?-aminoalkylphosphonate (DAP) organophosphorus inhibitor structure, seek to satisfy the need for a reactive yet specific mechanism for labeling chymotrypsin-like serine proteases in whole living cells