lysine

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lysine An essential amino acid of special nutritional importance, since it is the limiting amino acid in many cereals. Can be synthesized on a commercial scale, and when added to bread, rice, or cereal‐based animal feeds, it improves the nutritional value of the protein.

Not all of the lysine in proteins is biologically available, since some is linked through its side‐chain amino group, either to sugars (see Maillard reaction), or to other amino acids. These linkages are not hydrolysed by digestive enzymes, and so the lysine cannot be absorbed. Available lysine is that proportion of the protein‐bound lysine in which the side‐chain amino group is free, so that it can be absorbed after digestion of the protein.

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