1 National Institute of Aquatic Resources, Technical University of Denmark2 Section for Aquatic Protein Biochemistry, National Institute of Aquatic Resources, Technical University of Denmark3 Department of Systems Biology, Technical University of Denmark4 National Food Institute, Technical University of Denmark
A new and simple method to distinguish between cathepsin B and cathepsin L in crude extracts of herring (Clupea harengus) muscle has been established. An acid treatment of crude extracts (exposed to pH 3 for 5 min) activated a latent form of cathepsin L and inactivated cathepsin B. Furthermore, in neutral crude extract, the hydrolysis of benzyloxycarbonyl-L-phenylalanyl-L-arginyl-4-methylcoumarine (Z-Phe-Arg-MCA) (cathepsin B and cathepsin L substrates) was between 0% and 15% of the hydrolysis of benzyloxycarbonyl-L-arginyl-L-arginyl-7-amino-4-methylcoumarine (Z-Arg-Arg-MCA; cathepsin B substrate). Cathepsin B activity is measured in neutral extract using the specific cathepsin B substrate Z-Arg-Arg-MCA and cathepsin L activity is measured in acid-treated extract with Z-Phe-Arg-MCA as substrate. The specific cathepsin B inhibitor, CA-074, did not inhibit the Z-Arg-Arg-MCA significantly without affecting the Z-Phe-Arg-MCA activity. An acid treatment of the crude extract is therefore a more advantageous approach to discriminate between cathepsin B and cathepsin L activities.
International Journal of Food Science and Technology, 2007, Vol 42, Issue 1, p. 102-106