Glycomacropeptide (GMP) is a glycosolated peptide formed during renneting as a fragment of sweet

whey Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of hard ...

. Acid whey from yogurt or curdling cheese without the use of rennet does not contain GMP. The unglycosolated form is known as caseinomacropeptide or CMP. Both forms exist in roughly similar amounts in whey. Together GMP and CMP make up 20-25% of whey protein. This makes them the third largest fraction of

whey protein isolate Whey protein is a mixture of proteins isolated from whey, the liquid material created as a by-product of cheese production. The proteins consist of α-lactalbumin, β-lactoglobulin, serum albumin and immunoglobulins. Glycomacropeptide also makes ...

, after

alpha-lactalbumin Lactalbumin, alpha-, also known as LALBA, is a protein that in humans is encoded by the ''LALBA'' gene. Overview α-Lactalbumin is a protein that regulates the production of lactose in the milk of almost all mammalian species. In primates, alp ...

and

beta-lactoglobulin β-Lactoglobulin (BLG) is the major whey protein of cow and sheep's milk (~3 g/L), and is also present in many other mammalian species; a notable exception being humans. Its structure, properties and biological role have been reviewed many times. ...

. GMP is formed when the casein micelle that encapsulates milk protein is cleaved by the enzyme chymosin. The 64 terminal polypeptides of Kappa-casein are removed by the enzyme to create GMP. The remaining peptides form para-kappa-casein.{{cite journal , last1=Córdova , first1=Dávalos , title=Glycomacropeptide Bioactivity and Health: A Review Highlighting Action Mechanisms and Signaling Pathways , journal=Nutrients , date=March 11, 2019 , volume=11 , issue=3 , page=598 , doi=10.3390/nu11030598 , pmid=30870995 , pmc=6471465 , doi-access=free Vegetable rennets cleave at the same location and thus also produce GMP.

Properties

GMP is unique from other milk peptides in several ways. Kappa-casein is the only glycosolated casein protein and GMP, which makes up much of Kappa-casein, is also glycosolated. The glycans make GMP the only portion of the casein micelle that is water soluble after curdling has occurred, and thus, the only fraction of casein protein to dissolve into the whey. Additionally, GMP is the only easily attainable source of dietary peptides that does not contain any

aromatic amino acids An aromatic amino acid is an amino acid that includes an aromatic ring. Among the 20 standard amino acids, the following are classically considered aromatic: phenylalanine, tryptophan and tyrosine. Although histidine contains an aromatic ring, ...

. This makes it a safe source for individuals with

phenylketonuria Phenylketonuria (PKU) is an inborn error of metabolism that results in decreased metabolism of the amino acid phenylalanine. Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also resu ...

to obtain dietary amino acids, as

phenylalanine Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...

is an aromatic amino acid.

References

Peptides