Carboxyglutamic acid is an uncommon amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 introduced into proteins by a post-translational

Posttranslational modification

Posttranslational modification is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins....

 carboxylation

Carboxylation

Carboxylation in chemistry is a chemical reaction in which a carboxylic acid group is introduced in a substrate. The opposite reaction is decarboxylation.-Carboxylation in organic chemistry:In organic chemistry many different protocols exist for carboxylation...

 of glutamic acid

Glutamic acid

Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...

 residues. This modification is found, for example, in clotting factor

Coagulation

Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

s and other proteins of the coagulation cascade. This modification introduces an affinity for calcium ions

Calcium in biology

Calcium plays a pivotal role in the physiology and biochemistry of organisms and the cell. It plays an important role in signal transduction pathways, where it acts as a second messenger, in neurotransmitter release from neurons, contraction of all muscle cell types, and fertilization...

. In the blood coagulation cascade, Vitamin K

Vitamin K

Vitamin K is a group of structurally similar, fat soluble vitamins that are needed for the posttranslational modification of certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue. They are 2-methyl-1,4-naphthoquinone derivatives...

is required to introduce gamma-carboxylation of clotting factors II, VII, IX, and X.