Ca²⁺ as activator of pseudoperoxidase activity of pigeon, Eurasian woodcock and chicken myoglobins: New features for meat preservation studies

Myoglobin (Mb), hemeprotein that binds dioxygen in muscle, affects meat colour. Moreover, in presence of peroxides, metMb is a potent oxidant involved in oxidative rancidity in meat. Here, following pigeon Mb purification and primary structure mass spectroscopy characterization, we determined its autoxidation rate and pseudoperoxidase activity with respect to chicken and E. woodcock Mbs. The three Mbs exhibit different autoxidation rates (0.153-h^-1 pigeon, 0.194-h^-1 chicken and 0.220-h^-1 E. woodcock Mbs) and similar specificity constant (9.86x10³ M^-1s^-1 pigeon, 8.81x10³ M^-1s^-1 chicken and 9.90x10³ M^-1s^-1 E. woodcock Mbs), considering their pseudoperoxidase activity. Moreover, for the first time, we detected an increase in pseudoperoxidase activity in presence of Ca²⁺, particularly at pH 5.8. NMR and CD data indicate that the nonspecific Ca²⁺ binding induces small local structural rearrangements that in turn slightly reduce pigeon Mb thermal stability. However, considering Ca²⁺ concentration variations before and post-mortem, this finding must be considered for meat preservation.