Bovine intracellular cysteine proteinases

Cathepsins B, H and S were isolated from bovine lymph nodes and bovine spleen. It was shown that the incubation of homogenate at 37 degrees C at acid pH increased the total BANA hydrolase activity and LeuNA activity, whereas it decreased the total activity of cathepsin S. All three enzymes are electrophoretically homogeneous and probably composed of a single polypeptide chain. They exist in multiple forms as shown by isoelectric focusing. Far UV CD spectra revealed a rather high percentage of unordered structure. The three cysteine proteinases were inhibited by thiol blocking reagents, leupeptin and by an inhibitor isolated from Vipera ammodytes venom. Results on the specificity toward various substrates and the influence of pH on enzymatic activity are presented.