title: Chemical modification of the carboxyl groups of protein substrates enhances their thrombin susceptibility.
abstract: Native or denatured protein substrates which are hardly digested by thrombin can become much more efficiently cleaved by the enzyme after chemical modification of their carboxyl groups. Five antibody kappa-chains were used to demonstrate this effect. The selective cleavage sites were determined by quantitative N-terminal analysis and N-terminal sequencing. All five kappa-chains share the same cleavage sites at Arg-Thr (residues 108-109), Arg-Glu (residues 142-143, Glu side chain modified with glycine amide), Lys-Ser (residues 207-208) and Arg-Gly (residues 211-212). One of the major cleavage sites (Arg-Thr) is located at the joint of the variable/constant region. The amino acids adjacent to these cleavage sites underline the proposed structural requirements for a potential thrombin substrate [(1985) Eur. J. Biochem. 151, 217-224]. This approach can facilitate the application of thrombin in generating large polypeptide fragments of proteins.
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D007145:Immunoglobulin kappa-Chains; D007700:Kinetics; D010084:Oxidation-Reduction; D013379:Substrate Specificity; D013917:Thrombin / Q000378:metabolism*
chemical_list: D007145:Immunoglobulin kappa-Chains; D013917:Thrombin