Glycomacropeptide

Glycomacropeptide (GMP) is a peptide fragment derived from milk κ-casein during cheese production. It is produced when the enzyme chymosin cleaves κ-casein in the rennet coagulation process, releasing the glycosylated C-terminal portion into whey.

GMP is a relatively small, glycosylated peptide consisting of about 64 amino acids and bearing carbohydrate moieties. It is typically soluble in water and is enriched in whey fractions obtained during cheese making. The glycosylation distinguishes GMP from many other milk proteins and contributes to its distinctive functional properties.

Nutritional and medical relevance centers on its low phenylalanine content. GMP is of particular interest for phenylketonuria (PKU) dietary management because it can serve as a protein substitute with reduced phenylalanine. However, GMP is not a complete protein and is deficient in several essential amino acids, so products containing GMP are often formulated with added amino acids or used in combination with other protein sources to meet overall amino acid requirements. In practice, GMP is commonly used in specialized medical foods and dietary products for PKU.

Production and applications: GMP is recovered from cheese whey as a byproduct of cheese manufacture and is used in functional foods, dietary supplements, and medical foods. Ongoing research investigates potential additional roles for GMP, including prebiotic effects and interactions with gut function, though findings are not yet conclusive.