Amino acid sequence of human liver cathepsin B

The complete amino acid sequence of Cathepsin B (EC 3.4.22.1) from human liver was determined. The 252-residue sequence was obtained by automated solid-phase Edman degradation of the light and heavy chain resulting from limited proteolysis of the single-chain Enzyme and of fragments produced by cyanogen bromide and enzymatic cleavage of the heavy chain. Human liver Cathepsin B has 83.7% identical residues with the corresponding Enzyme from rat liver. Comparison of both mammalian Cathepsin B sequences with the sequence of papain provides further evidence that lysosomal and plant cysteine proteinases have evolved from a common ancestor and share a similar catalytic mechanism.