Mild oxidation promotes myosin S2 cross-linking by microbial transglutaminase

Area of Science:

• Food Science
• Protein Chemistry
• Meat Science

Background:

• Myosin cross-linking is crucial in meat processing.
• Previous studies focused on myofibril systems, addressing microbial transglutaminase (MTG) and free radicals.
• Understanding oxidation's impact on myosin is vital for meat quality.

Purpose of the Study:

• To investigate the effect of oxidation on the cross-linking of purified pork myosin by MTG.
• To determine how varying levels of hydrogen peroxide (H2O2) and iron (Fe) influence MTG-mediated cross-linking.
• To identify changes in myosin cross-linking sites under oxidative stress.

Main Methods:

• Purified pork Longissimus myosin was oxidized using H2O2 and Fe.
• Oxidized and non-oxidized myosin samples were treated with MTG at a 1:20 enzyme-to-substrate ratio.
• Cross-linking was quantified using ε(γ-glutamyl)lysine bond analysis, SDS-PAGE, and solubility tests.

Main Results:

• Mild oxidation (1 mM H2O2) significantly increased MTG cross-linking to 87.6%, compared to 64.7% in non-oxidized myosin.
• Excessive oxidation (200 mM H2O2) drastically reduced cross-linking to 33.8%.
• The S1 subfragment remained the primary cross-linking site, but the S2 subfragment became a significant site under mild oxidation.

Conclusions:

• Oxidation status critically modulates MTG cross-linking efficiency in purified myosin.
• Mild oxidation can enhance myosin cross-linking, potentially beneficial for meat processing.
• Findings provide insights for applying MTG in meat processing environments with uninhibited oxidation.