Myofibrillar protein from pork
Longissimus muscle was oxidatively stressed for 2 and 24 h at 4 掳C with mixed 10 渭M FeCl
3/100 渭M ascorbic acid/1, 5, or 10 mM H
2O
2 (which produces hydroxyl radicals) and then treated with microbial transglutaminase (MTG) (E:S = 1:20) for 2 h at 4 掳C. Oxidation induced significant protein structural changes (
P < 0.05) as evidenced by suppressed K-ATPase activity, elevated Ca-ATPase activity, increased carbonyl and disulfide contents, and reduced conformational stabi
lity, all in a H
2O
2 dose-dependent manner. The structural alterations, notably with mild oxidation, led to stronger MTG catalysis. More substantial amine reductions (19.8鈥?7.6%) at 1 mM H
2O
2 occurred as compared to 11.6% in nonoxidized samples (
P < 0.05) after MTG treatment. This coincided with more pronounced losses of myosin in oxidized samples (up to 33.2%) as compared to 21.1% in nonoxidized (
P < 0.05), which was attributed to glutamine鈥搇ysine cross-
linking as suggested by sodium dodecyl sulfate鈥損olyacrylamide gel electrophoresis.
Keywords:
myofibrillar protein;
protein oxidation;
transglutaminase;
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