Biomaterial Database

Evidence for a two-state transition in papain that may have no close analogue in ficin. Differences in the disposition of cationic sites and hydrophobic binding areas in the active centres of papain and ficin. 1980

K Brocklehurst, and J P Malthouse

The kinetics of the reactions of the active-centre thiol groups of papain (EC 3.4.22.2) and ficin (EC 3.4.22.3) with the two-protonic-state reactivity probes 2,2'-dipyridyl disulphide, n-propyl 2-pyridyl disulphide and 4-(N-aminoethyl 2'-pyridyl disulphide)- 7-nitrobenzo-2-oxa-1,3-diazole (compound I) were studied over a wide range of pH. Differences between the reactivities of ficin and papain towards the cationic forms of the alkyl 2-pyridyl disulphide probes suggest that ficin contains a cationic site without exact analogue in papain, and the striking difference in the shapes of the pH-rate profiles for the reactions of the two enzymes with compound (1) suggests differences in the mobilities or dispositions of the active-centre histidine imidazole groups with respect to relevant hydrophobic binding areas. The evidence from reactivity-probe studies that the papain catalytic mechanism involves substantial repositioning of the active-centre imidazole group during the catalytic act does not apply also to ficin. If ficin contains an aspartic acid residue analogous to aspartic acid-158 in papain, the pKa of its carboxy group is probably significantly lower than the pKa of the analogous group in papain.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008956	Models, Chemical	Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Chemical Models,Chemical Model,Model, Chemical
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
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D011725	Pyridines	Compounds with a six membered aromatic ring containing NITROGEN. The saturated version is PIPERIDINES.
D002621	Chemistry	A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
D004220	Disulfides	Chemical groups containing the covalent disulfide bonds -S-S-. The sulfur atoms can be bound to inorganic or organic moieties.	Disulfide
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