Abstract
The action of human plasma factor XIIIa (thrombin-activated blood coagulation factor XIII) and guinea pig liver transglutaminase on purified caseins, fibrin, the derivatized gamma chain of fibrin, and a number of synthetic glutamine peptides, and peptide derivatives is reported. There are wide variations in the properties of the individual proteins and peptides as substrates for amine incorporation by the two transglutaminases. beta-Casein and several of its derivatives are excellent substrates for factor XIIIa. However, beta-casein is a relatively poor substrate for the liver enzyme. The primary site of amine incorporation by factor XIIIa in beta-casein was identified as glutamine 167. This was accomplished by labeling with fluorescent amine followed by proteolytic digestion and identification of labeled peptides. An 11-residue peptide and a 15-residue peptide, each containing 1 glutamine residue and each modeled after the primary site of amine incorporation in beta-casein, were prepared. A 13-residue peptide modeled after the primary crosslinking site in fibrin gamma chain was also prepared. Each of these polypeptides proved to be an efficient substrate for factor XIIIa and displayed significantly better substrate properties than a number of small glutamine peptide derivatives that are good substrates for liver transglutaminase.
Highlights
Activated blood coagulation factor XIII) and guinea pig A study was undertaken in an effort to define the basis for liver transglutaminase on purified caseins, fibrin, the the differences in specificity of the transglutaminases with derivatized y chain of fibrin, and a number of synthetic special emphasis toward an understanding of the relatively glutamine peptides, and peptide derivatives is re- limited specificity of factor XIIIa
The primary site of amine incorporation by factor XIIIa in p-casein was identified as glutamine 167.This was accomplished by labeling with fluorescent amine followed by proteolytic digestion and identification of labeled peptides
An 11-residue peptide and a 15-residue peptide, each containing 1 glutamine residue and each modeled after the primary site of amine incorporation in p-casein, were prepared
Summary
A 13-residue peptide modeled after the primary crosslinking site in fibrin y chain wasalso be an excellent substrate for factor XIIIa, buat relativelypoor substrate for guinea pig liver transglutaminase [4]. This communication reports the position of the glutamine residue of p-casein most susceptible to the action of factor XIIIa and compares the substrate propertieosf several enzymically and synthetically prepared fragmentosf ,&casein that contain this glutamine residue. Transglutaminases catalyze the hydrolysis and aminolysis lated y chain of human fibrin In this miniprint supplement are of the y-carboxamide group of peptide-bound glutamine residues
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