Application of in-gel protease assay in a biological sample: characterization and identification of urokinase-type plasminogen activator (uPA) in secreted proteins from a prostate cancer cell line PC-3.

A considerable problem in proteomics is to separate and identify functional proteins that participate in specific biological processes. To expedite the analysis of active proteases, we have developed a substrate-specific, sensitive in-gel trypsin activity assay after two-dimensional (2-D) separation in a sodium dodecyl sulphate (SDS)-polyacrylamide gel [22]. Using this method, we detected and characterized Arg-specific protease activity in the secreted protein sample of a prostate cancer cell line, PC-3, in 1-D and 2-D gels.