cysteine-type peptidase activity Reactome:R-HSA-5660752 cysteine protease activity GO:0008234 GO:0004220 molecular_function thiol protease activity Reactome:R-HSA-2467809 Reactome:R-HSA-2022381 Catalysis of the hydrolysis of peptide bonds in a polypeptide chain by a mechanism in which the sulfhydryl group of a cysteine residue at the active center acts as a nucleophile. Reactome:R-HSA-2467775 peptidase activity, acting on L-amino acid peptides