Cathepsin V (EC 3.4.22.43, Cathepsin L2, cathepsin U) is an enzyme that catalyses the following chemical reaction: Cathepsin V (EC 3.4.22.43, Cathepsin L2, cathepsin U) is an enzyme that catalyses the following chemical reaction: The recombinant enzyme hydrolyses proteins (serum albumin, collagen) and synthetic substrates (Z-Phe-Arg-NHMec > Z-Leu-Arg-NHMec > Z-Val-Arg-NHMec) Cathepsin V is a human lysosomal cysteine endopeptidase.