ENTRY       EC 3.4.22.2
NAME        Papain
            Papaya peptidase I
            Calotropin
            Phytolacin
            Mexicanain
CLASS       Hydrolases
            Acting on peptide bonds (peptidases)
            Cysteine endopeptidases
REACTION    Hydrolysis of proteins with broad specificity for peptide bonds,
            with preference for a residue bearing a large hydrophobic
            sidechain at the P2 position.  Does not accept Val at P1'
SUBSTRATE   Protein
            Peptide
            H2O
PRODUCT     Protein
            Peptide
COMMENT     From latex of the papaya (Carica papaya).  Formerly EC 3.4.4.10.
            Many other plants contain cysteine endopeptidases, all of which
            seem to be homologues of papain, often with similar specificity.
            Examples not listed separately here are calotropin from the madar
            plant (Calotropis gigantea), phytolacin from the pokeweed
            (Phytolacca americana) and mexicanain from Pileus mexicanus
            (formerly EC 3.4.99.14).
MOTIF       PS: PS00139  Q-x(3)-[GE]-x-C-[YW]-x(2)-[STAGC]-[STAGCV]
            PS: PS00639  [LIVMGSTAN]-x-H-[GSACE]-[LIVM]-x-[LIVMAT](2)-G-x-
                         [GSADNH]
            PS: PS00640  [FYCH]-[WI]-[LIVT]-x-[KRQAG]-N-[ST]-W-x(3)-[FYW]-G-
                         x(2)-G-[LFYW]-[LIVMFYG]-x-[LIVMF]
STRUCTURES  PDB: 6PAD  1PAD  1PIP  1POP  1PPD  1STF  2PAD  4PAD  5PAD  9PAP  
DBLINKS     University of Geneva ENZYME DATA BANK: 3.4.22.2
            WIT (What Is There) Metabolic Reconstruction: 3.4.22.2
            SCOP (Structural Classificaion of Proteins): 3.4.22.2
///