An exopeptidase is any

peptidase A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the fo ...

that catalyzes the cleavage of the terminal (or the penultimate)

peptide bond In organic chemistry, a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 (nitrogen number two) of another, along a peptide or protein cha ...

; the process releases a single

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

dipeptide A dipeptide is an organic compound derived from two amino acids. The constituent amino acids can be the same or different. When different, two isomers of the dipeptide are possible, depending on the sequence. Several dipeptides are physiologicall ...

or a

tripeptide A tripeptide is a peptide derived from three amino acids joined by two or sometimes three peptide bonds. As for proteins, the function of peptides is determined by the constituent amino acids and their sequence. The simplest tripeptide is glycine ...

from the peptide chain. Depending on whether the amino acid is released from the amino or the carboxy terminal (

N-terminus The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...

C-terminus The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

), an exopeptidase is further classified as an aminopeptidase or a carboxypeptidase, respectively. Thus, an

aminopeptidase Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the amino terminus ( N-terminus) of proteins or peptides (exopeptidases). They are widely distributed throughout the animal and plant kingdoms and are found in many subcel ...

, an enzyme in the

brush border A brush border (striated border or brush border membrane) is the microvilli-covered surface of simple cuboidal and simple columnar epithelium found in different parts of the body. Microvilli are approximately 100 nanometers in diameter and the ...

of the

small intestine The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the p ...

, will cleave a single amino acid from the amino terminal, whereas

carboxypeptidase A carboxypeptidase ( EC number 3.4.16 - 3.4.18) is a protease enzyme that hydrolyzes (cleaves) a peptide bond at the carboxy-terminal (C-terminal) end of a protein or peptide. This is in contrast to an aminopeptidases, which cleave peptide bonds ...

, which is a

digestive enzyme Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anim ...

present in

pancreatic juice Pancreatic juice is a liquid secreted by the pancreas, which contains a number of digestive enzymes, including trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, pancreatic lipase, nucleases and amylase. The pancreas is located in the v ...

, will cleave a single amino acid from the carboxylic end of the peptide. Some examples of exopeptidases include: *

Carboxypeptidase A Carboxypeptidase A usually refers to the pancreatic exopeptidase that hydrolyzes peptide bonds of C-terminal residues with aromatic or aliphatic side-chains. Most scientists in the field now refer to this enzyme as CPA1, and to a related pancrea ...

- cleaves C-terminal Phe, Tyr, Trp, or Leu *

Carboxypeptidase B Carboxypeptidase B (, ''protaminase'', ''pancreatic carboxypeptidase B'', ''tissue carboxypeptidase B'', ''peptidyl-L-lysine -arginineydrolase'') is a carboxypeptidase that preferentially acts upon basic amino acids, such as arginine and lysi ...

- cleaves C-terminal Lys or Arg *

Aminopeptidase Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the amino terminus ( N-terminus) of proteins or peptides (exopeptidases). They are widely distributed throughout the animal and plant kingdoms and are found in many subcel ...

- cleaves any N-terminal amino acid *

Prolinase Cytosolic non-specific dipeptidase () also known as carnosine dipeptidase 2 is an enzyme that in humans is encoded by the ''CNDP2'' gene. This enzyme catalyses the following chemical reaction : Hydrolysis of dipeptides, preferentially hydrophobi ...

- cleaves N-terminal Pro from dipeptides *

Prolidase Xaa-Pro dipeptidase, also known as prolidase, is an enzyme that in humans is encoded by the ''PEPD'' gene. Function Xaa-Pro dipeptidase is a cytosolic dipeptidase that hydrolyzes dipeptides with proline or hydroxyproline at the carboxy termin ...

- cleaves C-terminal Pro from dipeptides

External links

References

EC 3.4 Enzymes {{hydrolase-stub

See also

External links

References