Biomaterial Database

Evidence for a close similarity in the catalytic sites of papain and ficin in near-neutral media despite differences in acidic and alkaline media. Kinetics of the reactions of papain and ficin with chloroacetate. 1982

K Brocklehurst, and S M Mushiri, and G Patel, and F Willenbrock

1. The pH-dependences of the second-order rate constants (k) for the alkylation by chloroacetate of the active-centre thiol groups of papain (EC 3.4.22.2) and ficin (EC 3.4.22.3) were determined over a wide range of pH at 25 degrees C at I 0.1. 2. The main feature of both pH-k profiles is a striking rate maximum at pH6 (characterizing parameters in both cases pKI approx. 3.5, pKII approx. 8.4 and pH-independent rate constant approximately kXH 2.5-3.0 M-1 . s-1). 3. The profile for the ficin reaction contains a plateau at high pH, with approximately kX 0.10 M-1 . s-1; if an analogous plateau exists in the papain reaction, approximately kX ix much lower, less than 0.02 M-1 . s-1. 4. Both enzymes appear to contain closely similar thiolate-imidazolium interactive systems at pH6, but differences in their behaviour in more-acidic media and in alkaline media suggest differences in interaction with the postulated carboxylate component of the putative catalytic triad.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010206	Papain	A proteolytic enzyme obtained from Carica papaya. It is also the name used for a purified mixture of papain and CHYMOPAPAIN that is used as a topical enzymatic debriding agent. EC 3.4.22.2.	Tromasin
D010450	Endopeptidases	A subclass of PEPTIDE HYDROLASES that catalyze the internal cleavage of PEPTIDES or PROTEINS.	Endopeptidase,Peptide Peptidohydrolases
D002384	Catalysis	The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.	Catalyses
D005361	Ficain	A sulfhydryl proteinase with cysteine at the active site from ficus latex. Preferential cleavage is at tyrosine and phenylalanine residues. EC 3.4.22.3.	Ficin
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000085	Acetates	Derivatives of ACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxymethane structure.	Acetate,Acetic Acid Esters,Acetic Acids,Acids, Acetic,Esters, Acetic Acid
D000478	Alkylation	The covalent bonding of an alkyl group to an organic compound. It can occur by a simple addition reaction or by substitution of another functional group.	Alkylations
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining