Effect of microbial transglutaminase on the natural actomyosin cross-linking in chicken and beef

The objective of this research was to investigate the difference between chicken and beef in the interaction of actomyosin (myosin B) with microbial transglutaminase (MTG). The gel strength of myosin B was improved in both species and was significantly greater in beef than in chicken (P < 0.01). The degree of protein viscosity and the ε(γ-glutamyl)lysine (G–L) content were significantly higher in beef than in chicken (P < 0.01). Myosin heavy chain (MHC) bands visualized by SDS–PAGE revealed that the same proteins in various meat species vary in their size and structure. Scanning electron microscope images (SEMI) revealed that myosin B in both species was polymerized, and formed multi-projection structures of G–L; surprisingly, more of these structures were found in beef than in chicken. It is possible that the proteins in chicken are folded into a strand shape that tightly encases a considerable number of glutamine and lysine residues, whereas MTG substrate cannot couple glutamine and lysine. This suggests that the reactivity of MTG is dependent on the residual amino acids present on the surface of myosin B in meat. Some protein components (peptides with long reiterated methylene groups attached) joined by disulfide bonds (cysteine) in chicken samples were inhibitory and reduced MTG activity. SEMI also suggested that all MTG-dependent mega-structures of protein molecules generated in chicken and beef may vary greatly in size, configuration and complexity after treatment with MTG. We concluded that the optimal cross-links in myosin B induced by MTG are heterogeneous in chicken and beef.