Table 10.4 Detection limits of the EnzChek Protease Assay Kits.

Enzyme (Source) Class Detection Limit (Units) * Buffer Conditions
Elastase, Type IV (porcine pancreas) Serine protease 2.2 × 10-3 10 mM Tris-HCl, pH 8.8
Chymotrypsin, Type II (bovine pancreas) Serine protease 5.0 × 10-5 10 mM Tris-HCl, pH 7.8
Thermolysin (Bacillus thermoproteolyticus Rokko) Acid protease 4.4 × 10-5 10 mM Tris-HCl, pH 7.8
Trypsin, Type IX (porcine pancreas) Serine protease 1.3 × 10-2 10 mM Tris-HCl, pH 7.8
Papain (papaya latex) Cysteine protease 2.1 × 10-4 10 mM MES, pH 6.2
Pepsin (porcine stomach mucosa) Acid protease 2.1 × 10-3 10 mM HCl, pH 2.0
Elastase (Pseudomonas aeruginosa) Metallo-protease 1.0 × 10-3 20 mM sodium phosphate, pH 8.0
Cathepsin D Acid protease 2.0 × 10-4 20 mM sodium citrate, pH 5.0
Elastase (human leukocyte) Serine protease 1.0 × 10-3 10 mM Tris-HCl, pH 7.5
* The detection limit is defined as the amount of enzyme required to cause a 10–20% change in fluorescence compared with the control sample at 22°C. Enzyme unit definitions are standard definitions for each individual enzyme. Detection limits were determined with BODIPY FL casein and with BODIPY TR-X casein; both substrates yielded similar results. Detection limits may vary with instrumentation.