Glycomacropeptide (GMP) is a casein-derived whey peptide. This peptide is released by rennet during the manufacture of cheese or rennet casein. Purified GMP and GMP-rich whey protein concentrates are currently available in the U.S. market. This product is sometimes also called caseinmacropeptide (CMP).

Beneficial biological roles attributed to GMP or peptides derived from it include stimulation of cholecystokinin (a hormone regulating energy and food intake) release from intestinal cells, inhibition of platelet aggregation and support of beneficial intestinal bacteria (i.e., bifidobacteria). Studies have also shown that GMP may help to reduce dental caries.

GMP-rich whey protein concentrate is also a good source of branched-chain amino acids, which have been shown to promote lean muscle development.

Glycomacropeptides contain no aromatic amino acids and no phenylalanine. This makes GMP suitable for diets in the treatment of patients with phenylketonuria.