Biomaterial Database

Modification of papain with tetranitromethane. 1978

S Tsukamoto, and M Ohno

Papain [EC 3.4.22.2] polymerizes readily upon treatment with tetranitromethane (TNM) by forming intermolecular covalent linkages through its tyrosine residues (Tsukamoto, S. & Ohno, M. (1974) J. Biochem. 75, 1377-1380). Polymerization occurred optimally at pH 9.0 with S-sulfenylsulfonate papain. Circular dichroic spectra of polymerized papains showed a small change in ellipticity when compared with that of unmodified papain. Esterolytic activity of the modified enzyme toward benzoyl-L-arginine ethyl ester (BAEE) was almost fully retained, at least up to the formation of hexamer, with an unchanged Km value. Spectrophotometric and amino acid analyses indicated that two or three tyrosine residues are involved in intermolecular crosslinks depending on the amount of TNM used. The tyrosine residues nitrated were identified as those at positions 61, 116, 103, and 4, the extent of nitration decreasing in this order. When activated papain was treated with increasing molar ratios of TNM, an essential sulfhydryl function was first oxidized and, at a 2-fold molar excess of the reagent, restoration of activity was no longer observed even after addition of dithiothreitol (DTT). The evidence obtained in the present study eliminates the possibility of inactivation due to nitration of a tryptophan residue, which had been suggested previously.

UI	MeSH Term	Description	Entries
D008697	Methane	The simplest saturated hydrocarbon. It is a colorless, flammable gas, slightly soluble in water. It is one of the chief constituents of natural gas and is formed in the decomposition of organic matter. (Grant & Hackh's Chemical Dictionary, 5th ed)
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
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
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
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D004229	Dithiothreitol	A reagent commonly used in biochemical studies as a protective agent to prevent the oxidation of SH (thiol) groups and for reducing disulphides to dithiols.	Cleland Reagent,Cleland's Reagent,Sputolysin,Clelands Reagent,Reagent, Cleland,Reagent, Cleland's
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
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
D013774	Tetranitromethane	Corrosive oxidant, explosive; additive to diesel and rocket fuels; causes skin and lung irritation; proposed war gas. A useful reagent for studying the modification of specific amino acids, particularly tyrosine residues in proteins. Has also been used for studying carbanion formation and for detecting the presence of double bonds in organic compounds.