3.4.23.B9 The best substrate YDPPAILPII is bearing the natural cleavage site between the matrix and the capsid proteins of BLV Gag precursor. polyprotein. Good cleavage of the peptide bonds: Leu-Pro, Leu-Val, Gly-Val and Leu-Pro - - 3.4.23.B9 The best substrate YDPPAILPII is bearing the natural cleavage site between the matrix and the capsid proteins of BLV Gag precursor. polyprotein. Good cleavage of the peptide bonds: Leu-Pro, Leu-Val, Gly-Val and Leu-Pro the enzyme contains the aspartic protease sequence Asp-Thr-Gly -, 668796