Isolation of novel peptides, cabin-1, -2, -3, and -4, that inhibit cathepsin B from a thermolysin digest of human plasma.

Four novel peptides that inhibit cathepsin B, designated as Cabin-1, -2, -3, and -4, were isolated from a thermolysin digest of human plasma. After gel filtration and cation-exchange chromatography, the peptide mixture was purified by reverse-phase HPLC to isolate Cabin-1, -2, -3, and 4, with the amino acid sequences LGPVTQE, VLQSSGLYS, VVSVLT, and LVYDAY, respectively. These peptides correspond to f(64-70) of human apolipoprotein A-I for Cabin-1, f(56-64) and f(185-190) of the human immunoglobulin G gamma chain for Cabin-2 and -3, and f(66-71) of human transferrin for Cabin-4.