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Myoglobin species with enhanced prooxidative activity is formed during mild proteolysis by pepsin

Charlotte U Carlsen1, Leif H Skibsted

  • 1Department of Dairy and Food Science, Food Chemistry, Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.

Journal of Agricultural and Food Chemistry
|March 20, 2004
PubMed

Insights

Pepsin proteolysis of metmyoglobin reduced its peroxidase activity but enhanced its prooxidative effect on lipid oxidation. Mildly altered metmyoglobin stabilized iron(II), suggesting a role in lipid peroxidation radicals.

Area of Science:

  • Food Science
  • Biochemistry
  • Protein Chemistry

Background:

  • Metmyoglobin is a key protein in meat color and oxidation.
  • Understanding protein modifications is crucial for food quality and safety.

Purpose of the Study:

  • To investigate the impact of pepsin proteolysis on metmyoglobin's peroxidase and prooxidative activities.
  • To elucidate the mechanisms behind altered metmyoglobin activity after mild enzymatic modification.

Main Methods:

  • Pepsin proteolysis of metmyoglobin at different pH values.
  • Assessing peroxidase activity using hydrogen peroxide (H2O2) and ABTS.
  • Measuring lipid oxidation in methyl linoleate emulsions via oxygen depletion rates.
  • Analyzing spectral characteristics and effects of chelators and scavengers.

Main Results:

  • Mild pepsin proteolysis (pH ~4) decreased metmyoglobin's peroxidase activity.
  • Mild proteolysis significantly enhanced metmyoglobin's prooxidative effect on lipid oxidation.
  • Severe proteolysis did not yield similar prooxidative enhancement.
  • Spectral data indicated stabilization of the iron(II) state in mildly proteolyzed metmyoglobin.

Conclusions:

  • Mild pepsin proteolysis alters metmyoglobin's redox properties, enhancing its prooxidative capacity.
  • The enhanced prooxidative effect is linked to iron(II)/iron(III) cycling at the lipid-water interface, promoting lipid peroxide radical formation.
  • Enzymatic modification of metmyoglobin can influence lipid oxidation pathways in food systems.

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