Myoglobin Post-Translational Modifications Influence Color Stability of Beef Longissimus Lumborum

Abstract

Post-translational modifications (PTM) of proteins play critical roles in biological processes. PTM of muscle proteins influence meat quality. Nonetheless, myoglobin (Mb) PTM and their impact on fresh beef color stability have not been characterized yet. Therefore, our objectives were to identify Mb PTM in beef longissimus lumborum muscle during postmortem aging and to characterize their influence on color stability. The longissimus lumborum muscles from 9 (n = 9) beef carcasses (24 h postmortem) were subjected to wet aging for 0, 7, 14, and 21 d. At the end of each wet-aging period, steaks were fabricated. One steak for analyses of PTM was immediately frozen at −80°C, whereas other steaks were assigned to refrigerated storage in the darkness under aerobic packaging. Instrumental color and biochemical attributes were evaluated on day 0, 3, or 6 of storage. Mb PTM were analyzed using two-dimensional electrophoresis and tandem mass spectrometry. Surface redness (a* value), color stability, and Mb concentration decreased (P < 0.05) upon aging. Gel image analyses identified 6 Mb spots with similar molecular weight (17 kDa) but different isoelectric pH. Tandem mass spectrometry identified multiple PTM (phosphorylation, methylation, carboxymethylation, acetylation, and 4-hydroxynonenal alkylation) in these 6 isoforms. The amino acids susceptible to phosphorylation were serine (S), threonine (T), and tyrosine, whereas other PTM were detected in lysine (K), arginine (R), and histidine residues. Additionally, distal histidine (position 64), critical to heme stability, was found to be alkylated. Overall, Mb PTM increased with aging. The aging-induced PTM, especially those occurring close to hydrophobic heme pocket, could disrupt Mb tertiary structure, influence heme affinity, and compromise oxygen binding capacity, leading to decreased color stability of fresh beef. Furthermore, PTM at K45, K47, and K87 were unique to Mb from non-aged beef, whereas PTM at R31, T51, K96, K98, S121, R139, and K147 were unique to Mb from aged counterparts, indicating that these Mb PTM could be used as novel biomarkers for fresh beef color stability.

Lipid Peroxidation Products Influence Calpain-1 Functionality In Vitro by Covalent Binding

“…31 Likewise, in vitro and in vivo HNE adducts have been identified in cytoskeletal proteins, 57−59 metabolic enzymes, 60−62 chaperones, 63,64 membrane receptors, 65 regulatory proteins, 66,67 signaling proteins, 68−71 and transport proteins. 24,32,72 The increased levels of MDA and HNE adduction in proteins are also associated with acute and chronic diseases, 55,73 such as cardiovascular, Alzheimer's, Parkinson's, and liver diseases.…”

“…Malondialdehyde (MDA; 3-carbon), hexenal (6-carbon), and 4-hydroxynonenal (HNE; 9-carbon) are lipid-oxidation-derived aldehydes that have been identified in fresh meat under aerobic packaging . These aldehydes can cause protein lipoxidation by forming covalent bonds with proteins in meat, ,, and their reactivity varies with carbon number. , Therefore, the objective of the current study was to investigate the effect of lipid peroxidation products, MDA, hexenal, and HNE, on calpain-1 activity and autolysis in vitro coupled with liquid chromatography and tandem mass spectrometry (LC-MS/MS) identification of adducts on the protein. We hypothesized that calpain-1 activity would change after exposure to lipid peroxidation products, and these changes would be associated with the covalent binding of aldehydes on calpain-1.…”

Undesirable discoloration in edible fish muscle: Impact of indigenous pigments, chemical reactions, processing, and its prevention

“…The sixth domain of heme iron determines the color of the meat via binding to H 2 O (purple–red color), oxygen (bright red color), carbon monoxide (CO; bright red color), and nitric oxide (NO; bright cherry red color) (Cornforth & Jayasingh, 2004). The conjugated double bonds present in Mb (in the heme group) absorb visible light, thus imparting its color (Wang, 2020). In general, some fish have light or ordinary muscle, but in some species, the muscle tissue color is red or brown.…”

A meta-analysis of the effect of gamma irradiation on chicken meat quality: Microbiology and colour

“…The authors stated that during lipid oxidation a wide range of primary and secondary products are generated. They can adduct to histidine, lysine, and cysteine residues in myoglobin through alkylation and hence induce its oxidation (Wang et al 2021). When the central iron atom within the heme group of myoglobin is oxidized, the ferrous heme iron is converted to its ferric form, resulting in change from OxyMb to MetMb, which is responsible for meat discoloration (Faustman et al 2010).…”