Post-translational modification represents various functional groups that are added to proteins following translation. The addition of functional groups to amino acids influences structure and function of proteins. Although post-translational modification in myoglobin from normal beef is reported, limited knowledge is currently available on myoglobin post-translation modifications in high-pH beef. Therefore, the overall goal of this study was to determine the extent of post-translation modifications in myoglobin from high-pH beef compared with myoglobin from normal-pH beef. Eight (n = 8) normal-pH and high-pH dark-cutting beef carcasses (24 h postmortem) were selected from a commercial beef processor. The normal-pH (pH = 5.4) and high-pH (pH = 6.8) beef loins (longissimus lumborum muscles) were selected based on the pH values to determine post-translational modification in myoglobin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to separate myoglobin from other sarcoplasmic proteins. The protein band (17 kDa) representing myoglobin in the gels was excised and subjected to in-gel tryptic digestion. The tryptic peptides were extracted, concentrated, and subjected to liquid chromatography-electrospray ionization-tandem mass spectrometry. Mass spectrometric data were analyzed using Proteome Discoverer for identification of post-translational modifications such as methionine oxidation; lysine acetylation; lysine mono-, di-, and tri-methylation; arginine mono- and dimethylation; lysine carboxymethylation; serine, threonine and tyrosine phosphorylation; 4-hydroxynonenal (HNE) alkylation at histidine, and lysine. Tandem mass spectrometry identified phosphorylation, acetylation, carboxymethylation, and mono-, di-, and tri-methylation in normal-pH and high-pH beef myoglobins. In normal-pH beef myoglobin seven lysines were acetylated, while 11 lysine sites were acetylated in myoglobin from high-pH beef. Similarly, seven sites were phosphorylated in normal-pH myoglobin, while 10 sites were modified in high-pH myoglobin. Carboxymethylation, mono-, di- and tri-methylation also demonstrated differential modifications between normal- and high-pH beef myoglobins. In summary, postmortem muscle pH influences the extent of post-translational modifications in beef myoglobin. The binding of functional groups to myoglobin, in part, can influence oxygen binding and contribute to darker meat color.

Myoglobin post-translational modifications in high- and normal-pH beef

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.