Carlsen Charlotte U, Skibsted Leif H
Department of Dairy and Food Science, Food Chemistry, Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.
J Agric Food Chem. 2004 Mar 24;52(6):1675-81. doi: 10.1021/jf030494u.
Pepsin proteolysis at pH approximately 4 resulted in a lowering of the (pseudo)peroxidase activity of metmyoglobin both at physiological pH and at meat pH, as measured by a peroxidase assay with H(2)O(2) and ABTS as substrates. In contrast, the mildly proteolyzed myoglobin had a strongly enhanced prooxidative effect on lipid oxidation in an oil in water methyl linoleate emulsion compared to native metmyoglobin, as evidenced by rates of oxygen depletion. More severe proteolysis of metmyoglobin at lower pH values near the optimum for pepsin did not result in a similar enhancement of prooxidative activity. The mildly proteolyzed metmyoglobin had spectral characteristics in agreement with a relative stabilization of the iron(II) state. On the basis of the observed effects of metal chelators, of lipophilic and hydrophilic peroxides and of radical scavengers on oxygen depletion rates, it is suggested that the increased prooxidative effect is due to radicals formed by cleavage of lipid peroxides by iron(II)/iron(III) cycling of a heme pigment with affinity for the lipid/water interface.
在pH约为4的条件下，用胃蛋白酶进行蛋白水解，无论是在生理pH值还是肉的pH值下，通过以H₂O₂和ABTS为底物的过氧化物酶测定法测量，高铁肌红蛋白的（假）过氧化物酶活性均降低。相比之下，与天然高铁肌红蛋白相比，轻度蛋白水解的肌红蛋白对水包油型亚油酸甲酯乳液中的脂质氧化具有更强的促氧化作用，这一点通过氧气消耗速率得以证明。在接近胃蛋白酶最适pH值的较低pH值下对高铁肌红蛋白进行更剧烈的蛋白水解，并未导致促氧化活性有类似增强。轻度蛋白水解的高铁肌红蛋白的光谱特征与亚铁（II）状态的相对稳定一致。基于所观察到的金属螯合剂、亲脂性和亲水性过氧化物以及自由基清除剂对氧气消耗速率的影响，表明促氧化作用增强是由于具有脂质/水界面亲和力的血红素色素通过铁（II）/铁（III）循环裂解脂质过氧化物而形成的自由基所致。
