The case for assigning a value of approximately 4 to pKa-i of the essential histidine-cysteine interactive systems of papain, bromelain and ficin.
D001963:Bromelains / Q000378:metabolism; D003545:Cysteine; D010450:Endopeptidases / Q000378:metabolism; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010206:Papain / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors
D006639:Histidine; D001963:Bromelains; D010450:Endopeptidases; D010206:Papain; D003545:Cysteine