[Immunochemical study of bovine spleen thiol proteinases: cathepsinS B, H and L]

Rabbit antisera were prepared against three highly purified enzymes from bovine spleen: proteinase I (cathepsin L), proteinase II (cathepsin H), and cathepsin B. The Ouchterlony double diffusion test shows that each antiserum specifically reacts with the corresponding antigen and does not cross react with other proteinases. These data provide evidence that the three proteinases are distinct with respect to their antigenic properties. Using specific antisera, the identity of two preparations of proteinase I isolated by different methods was demonstrated. Analysis of the fractions obtained in the course of isolation procedure revealed a component reacting with antisera against proteinase I. It had a greater molecular mass than proteinase I (30 000-40 000), was richer in antigenic respect and had a lower proteolytic activity as compared with proteinase I. The effect of various inhibitors and denaturation conditions on antigenic properties of proteinases was also studied.