Procathepsin L-specific antibodies that recognize procathepsin L but not cathepsin L

Procathepsin L was purified to apparent homogeneity from the culture medium of v-Ha-ras transformed NIH3T3 (Ras-NIH) cells in three steps; anion-exchange chromatography, gel filtration, and re-gel filtration. SDS-PAGE analyses revealed that the purified samples contained only the precursor form, procathepsin L, but not the mature enzyme, cathepsin L. Antibodies against purified procathepsin L were raised. These recognized both rat cathepsin L and the purified procathepsin L. To isolate procathepsin L-specific antibodies that did not recognize cathepsin L, sequential affinity chromatography procedures were carried out. Immunoblot analyses showed that the procathepsin L-specific antibodies recognized only procathepsin L, but not cathepsin L.