Effect of Malondialdehyde on the Digestibility of Beef Myofibrillar Protein: Potential Mechanisms from Structure to Modification Site

Abstract

Lipid oxidation and protein oxidation occur side by side in meat. Here, the effect of malondialdehyde (MDA), the major product of lipid oxidation, on the digestibility of beef myofibrillar proteins (MP) was studied. MP samples were incubated with 0, 0.1, 0.3, 0.5, and 0.7 mM MDA at 4 °C for 12 h and then subjected to in vitro gastrointestinal digestion. The result showed that MDA remarkably reduced the digestibility of MP (p < 0.05). MDA treatments significantly increased carbonyl and Schiff base contents in MP (p < 0.05). The microstructure observed by atomic force microscopy showed that MDA treatments resulted in the aggregation of MP. Non-reducing and reducing electrophoresis suggested the aggregation was mainly caused by covalent bonds including disulfide bond and carbonyl–amine bond. Proteomics analysis proved that the myosin tail was the main target of MDA attack, meanwhile, lysine residues were the major modification sites. Taken together, the above results imply that MDA induces protein oxidation, aggregation, and blockage of hydrolysis sites, consequently leading to the decrease in both gastric and gastrointestinal digestibility of MP.

Molecular Mechanisms Underlying the Effect of Lipid Oxidation Products on Digestibility and Conformation of Myoglobin under Thermal Treatment

“…46 In this work, the intrinsic fluorescence intensity decreased with the addition of 2,4-Dec, which is partially attributed to 2,4-Dec binding to other sites on the protein (lysine, arginine, and histidine) and partially due to the folding of amino acids. 47 These results agree with the work of Traverso et al, finding the decreased fluorescence intensity due to the LOP binding to other sites in the protein results in reduced appearance of tryptophan in the aqueous environment. 48 Moreover, decreased intrinsic fluorescence is a sign of induced compact protein conformation and protein aggregation.…”

“…Intrinsic fluorescence can be used to infer structural variations in proteins since the intrinsic fluorescence of proteins is mainly due to the tryptophan and tyrosine; there are two tryptophan residues and two tyrosine residues within native Mb . In this work, the intrinsic fluorescence intensity decreased with the addition of 2,4-Dec, which is partially attributed to 2,4-Dec binding to other sites on the protein (lysine, arginine, and histidine) and partially due to the folding of amino acids . These results agree with the work of Traverso et al, finding the decreased fluorescence intensity due to the LOP binding to other sites in the protein results in reduced appearance of tryptophan in the aqueous environment .…”

Moderate Protein Oxidation Improves Bovine Myofibril Digestibility by Releasing Peptides in the S2 Region of Myosin: A Peptidomics Perspective

“…There are many hydrophobic amino acids in MP, such as tyrosine, alanine, and proline. These hydrophobic amino acids are usually buried in protein to maintain the stability of structure . It is widely accepted that moderate oxidation results in protein unfolding, while excessive oxidation causes aggregation of protein .…”

“…These hydrophobic amino acids are usually buried in protein to maintain the stability of structure. 22 It is widely accepted that moderate oxidation results in protein unfolding, while excessive oxidation causes aggregation of protein. 23 Thus, the increase of surface hydrophobicity suggested that oxidation treatment with 1 mM H 2 O 2 induced the unfolding of MP, which facilitated the accessibility of ANS to hydrophobic amino acids.…”

Possibility to Apply Strontium Aluminate to Produce Light‐Emitting Plants: Efficiency and Safety

“…Conversely, plants treated with SrAl 2 O 4 products 2 and 3 exhibited a decrease in pipecolic acid and salicylic acid around 0.005 and 0.061‐fold, respectively, compared to control plants. This decrease was attributed to the excess accumulation of MDA resulting from lipid peroxidation reactions, which activated protein oxidation, because MDA contains carbonyl groups that can attack nucleophilic amino acid side chains leading to reduction of lysine biosynthesis [55] . It can be observed that SrAl 2 O 4 product 2 treatment caused the highest toxicity to plants as evidenced by the failure of plant's defense mechanisms through the salicylic acid defense pathway.…”