Lysinoalanine Formation and Characterization in Food Proteins

Lysinoalanine is an unusual crosslinked amino acid formed when the ε-amine of lysine reacts with dehydroalanine residues generated by elimination reactions during processing. This post-translational modification arises under alkaline or high-temperature conditions, leading to the formation of covalent protein–protein bridges. The occurrence of lysinoalanine in food proteins has drawn attention due to its potential impact on nutritional quality, protein digestibility and metal-binding properties. The crosslink hinders proteolytic enzymes, reduces the bioavailability of lysine and can chelate essential metal ions, with implications for both human health and food safety. Characterisation of lysinoalanine in complex matrices remains a major analytical challenge owing to its low abundance and structural similarity to other amino acid modifications. Advances in mass spectrometry, chromatography and diagnostic ion discovery have begun to unravel the distribution of lysinoalanine in diverse food systems, from dairy isolates to plant-derived protein concentrates. A deeper understanding of its kinetics, formation pathways and inhibition strategies is critical for the food industry, particularly in the development of protein alternatives and in optimising thermal or alkaline extraction processes to preserve nutritional value.

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Lysinoalanine Formation and Characterization in Food Proteins publication trend

The graph below shows the total number of articles in lysinoalanine formation and characterization in food proteins across all publications each year (not limited to Nature Index journals).

Technical terms

Lysinoalanine: A crosslinked amino acid formed by reaction of lysine’s ε-amine with dehydroalanine, resulting in an irreversible protein–protein bond.

Dehydroalanine: A reactive unsaturated residue generated from serine or cysteine under heat or alkali, serving as a precursor for crosslink formation.

Matrix-Assisted Laser Desorption/Ionisation Mass Spectrometry (MALDI-MS): A technique that ionises peptides or proteins with minimal fragmentation, allowing detection of diagnostic ions.

Multiple Reaction Monitoring (MRM): A targeted mass spectrometry method that quantifies specific molecular transitions, enabling simultaneous measurement of multiple modification markers.

Maillard Reaction: A non-enzymatic browning pathway between reducing sugars and amino groups, yielding diverse flavour and colour compounds and competing with dehydroalanine pathways.

References

1. Characterizing lysinoalanine crosslinks in food systems: Discovery of a diagnostic ion in model peptides using MALDI mass spectrometry. Food Chemistry X (2023).
2. Influence of Lactose on the Maillard Reaction and Dehydroalanine-Mediated Protein Cross-Linking in Casein and Whey. Foods (2022).
3. Lysinoalanine as a metal chelator. An implication for toxicity.. Journal of Biological Chemistry (1982).
4. FACTORS AFFECTING THE AVAILABILITY OF LYSINE IN HEAT-PROCESSED CASEIN. Journal of Biological Chemistry (1948).