Erepsin is a mixture of

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s contained in a protein fraction found in the intestinal juices that digest peptones into

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

. It is produced and secreted by the

intestinal gland In histology, an intestinal gland (also Crypt (anatomy), crypt of Johann Nathanael Lieberkühn, Lieberkühn and intestinal crypt) is a gland found in between Intestinal villus, villi in the intestinal epithelium, intestinal epithelial lining of th ...

s in the

ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may ...

and the

pancreas The pancreas (plural pancreases, or pancreata) is an Organ (anatomy), organ of the Digestion, digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a ...

, but it is also found widely in other cells. However, the term now rarely used in scientific literature as more precise terms are preferred.

History

Erepsin was discovered at the beginning of the twentieth century by German physiologist Otto Cohnheim (1873-1953) who found a substance that breaks down peptones into amino acid in the intestines. He termed this hypothetical protease in his protein extract "erepsin" in 1901, derived from a Greek word meaning "I break down" (έρείπω). His discovery was significant as it overturned the previous "hypothesis of resynthesis" which proposed that proteins get broken down into peptones from which proteins may then be resynthesized, and helped establish the idea of free amino acids instead of peptones being the building blocks of protein. Erepsin was originally thought to be a single enzyme or a mixture of a few enzymes involved in the terminal stages of the breakdown of peptides to free amino acids in the intestines. However, it became clear later that erepsin is in fact a complex mixture of different peptidases. It was also found not to be unique to intestinal

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

and is present widely in many other cells and organisms. The term erepsin fell from use in scientific literature in the latter half of the twentieth century as scientists considered its use as a term for a single enzyme or a few enzymes misleading, and more precise terms such as

aminopeptidase Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the N-terminus (beginning), of proteins or peptides. They are found in many organisms; in the cell, they are found in many organelles, in the cytosol (internal cellular f ...

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 b ...

and dipeptidase are preferred. The term is now considered obsolete.

Properties

Erepsin may contain dipeptidases, aminopeptidases, occasionally carboxypeptidases, and these include leucyl aminopeptidase, prolinase, prolidase and others. It is often grouped under

exopeptidase An exopeptidase is any peptidase that catalyzes the cleavage of the terminal (or the penultimate) peptide bond; the process releases a single amino acid, dipeptide or a tripeptide from the peptide chain. Depending on whether the amino acid is r ...

s, proteases that work only on the outermost

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 ...

s of a polypeptide chain. The optimum pH for the group of enzymes is around pH 8, but some individual enzymes within this group may be distinguished by their differences in stability and optimum pH.

References

{{reflist Enzymes Obsolete medical terms