Erepsin

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Erepsin is a mixture of enzymes contained in a protein fraction found in the intestinal juices that digest peptones into amino acids. It is produced and secreted by the intestinal glands in the ileum and the pancreas, but it is also found widely in other cells. It is, however, a term now rarely used in scientific literature as more precise terms are preferred.

Contents

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. [1] [2] He termed this hypothetical protease in his protein extract "erepsin" in 1901, derived from a Greek word meaning "I break down" (έρείπω). [3] 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. [3]

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. [4] However, it became clear later that erepsin is in fact a complex mixture of different peptidases. [5] It was also found not to be unique to intestinal mucosa and is present widely in many other cells and organisms. [6] [7] [8] 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, [9] and more precise terms such as aminopeptidase, carboxypeptidase and dipeptidase are preferred. The term is now considered obsolete. [10]

Properties

Erepsin may contain dipeptidases, aminopeptidases, occasionally carboxypeptidases, and these include leucyl aminopeptidase, prolinase, prolidase and others. [5] It is often grouped under exopeptidases, proteases that work only on the outermost peptide bonds 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. [5]

Related Research Articles

<span class="mw-page-title-main">Peptide bond</span> Covalent chemical bond between amino acids in a peptide or protein chain

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

<span class="mw-page-title-main">Proteolysis</span> Breakdown of proteins into smaller polypeptides or amino acids

Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, but may also occur by intra-molecular digestion.

<span class="mw-page-title-main">Protease</span> Enzyme that cleaves other proteins into smaller peptides

A protease is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds. Proteases are involved in numerous biological pathways, including digestion of ingested proteins, protein catabolism, and cell signaling.

<span class="mw-page-title-main">Digestive enzyme</span> Class of enzymes

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 animals and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival. Digestive enzymes of diverse specificities are found in the saliva secreted by the salivary glands, in the secretions of cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells, and in the secretions of cells lining the small and large intestines.

<span class="mw-page-title-main">Alanine aminopeptidase</span> Mammalian protein found in Homo sapiens

Membrane alanyl aminopeptidase also known as alanyl aminopeptidase (AAP) or aminopeptidase N (AP-N) is an enzyme that in humans is encoded by the ANPEP gene.

An exopeptidase is any peptidase that catalyzes the cleavage of the terminal peptide bond; the process releases a single amino acid, dipeptide or a tripeptide from the peptide chain. Depending on whether the amino acid is released from the amino or the carboxy terminal, an exopeptidase is further classified as an aminopeptidase or a carboxypeptidase, respectively. Thus, an aminopeptidase, an enzyme in the brush border of the small intestine, will cleave a single amino acid from the amino terminal, whereas carboxypeptidase, which is a digestive enzyme present in pancreatic juice, will cleave a single amino acid from the carboxylic end of the peptide.

<span class="mw-page-title-main">Cysteine protease</span> Class of enzymes

Cysteine proteases, also known as thiol proteases, are hydrolase enzymes that degrade proteins. These proteases share a common catalytic mechanism that involves a nucleophilic cysteine thiol in a catalytic triad or dyad.

Kininogens are precursor proteins for kinins, biologically active polypeptides involved in blood coagulation, vasodilation, smooth muscle contraction, inflammatory regulation, and the regulation of the cardiovascular and renal systems.

<span class="mw-page-title-main">Aminopeptidase</span> Class of enzymes

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 subcellular organelles, in cytosol, and as membrane components. Aminopeptidases are used in essential cellular functions. Many, but not all, of these peptidases are zinc metalloenzymes.

Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism.

<span class="mw-page-title-main">Cathepsin D</span> Protein-coding gene in the species Homo sapiens

Cathepsin D is a protein that in humans is encoded by the CTSD gene. This gene encodes a lysosomal aspartyl protease composed of a protein dimer of disulfide-linked heavy and light chains, both produced from a single protein precursor. Cathepsin D is an aspartic endo-protease that is ubiquitously distributed in lysosomes. The main function of cathepsin D is to degrade proteins and activate precursors of bioactive proteins in pre-lysosomal compartments. This proteinase, which is a member of the peptidase A1 family, has a specificity similar to but narrower than that of pepsin A. Transcription of the CTSD gene is initiated from several sites, including one that is a start site for an estrogen-regulated transcript. Mutations in this gene are involved in the pathogenesis of several diseases, including breast cancer and possibly Alzheimer disease. Homozygous deletion of the CTSD gene leads to early lethality in the postnatal phase. Deficiency of CTSD gene has been reported an underlying cause of neuronal ceroid lipofuscinosis (NCL).

<span class="mw-page-title-main">PEPD</span> Protein-coding gene in the species Homo sapiens

Xaa-Pro dipeptidase, also known as prolidase, is an enzyme that in humans is encoded by the PEPD gene. Prolidase is an enzyme in humans that plays a crucial role in protein metabolism and collagen recycling through the catalysis of the rate-limiting step in these chemical reactions. This enzyme is coded by the gene PEPD, located on chromosome 19. Serum prolidase activity is also currently being explored as a biomarker for diseases.

<span class="mw-page-title-main">CPM (gene)</span> Protein-coding gene in humans

Carboxypeptidase M is an enzyme that in humans is encoded by the CPM gene.

<span class="mw-page-title-main">DPP7</span> Protein-coding gene in the species Homo sapiens

Dipeptidyl-peptidase 2 is an enzyme that in humans is encoded by the DPP7 gene.

<span class="mw-page-title-main">CPA3</span> Enzyme found in humans

Carboxypeptidase A3 (mast cell carboxypeptidase A), also known as CPA3, is an enzyme which in humans is encoded by the CPA3 gene. The "CPA3" gene expression has only been detected in mast cells and mast-cell-like lines, and CPA3 is located in secretory granules. CPA3 is one of 8-9 members of the A/B subfamily that includes the well-studied pancreatic enzymes carboxypeptidase A1 (CPA1), carboxypeptidase A2 (CPA2), and carboxypeptidase B. This subfamily includes 6 carboxypeptidase A-like enzymes, numbered 1-6. The enzyme now called CPA3 was originally named mast cell carboxypeptidase A, and another protein was initially called CPA3. A gene nomenclature committee renamed mast cell carboxypeptidase A as CPA3, and the original CPA3 reported by Huang et al. became CPA4 to reflect the order of their discovery.

<span class="mw-page-title-main">Aminopeptidase Y</span> Class of enzymes

Aminopeptidase Y is an enzyme. This enzyme catalyses the following chemical reaction

Methionyl aminopeptidase is an enzyme. This enzyme catalyses the following chemical reaction

Dipeptidyl-peptidase II is an enzyme. This enzyme catalyses the following chemical reaction:

<span class="mw-page-title-main">Peptidyl-dipeptidase Dcp</span> Class of enzymes

Peptidyl-dipeptidase Dcp (EC 3.4.15.5, dipeptidyl carboxypeptidase (Dcp), dipeptidyl carboxypeptidase) is a metalloenzyme found in the cytoplasm of bacterium E. Coli responsible for the C-terminal cleavage of a variety of dipeptides and unprotected larger peptide chains. The enzyme does not hydrolyze bonds in which P1' is Proline, or both P1 and P1' are Glycine. Dcp consists of 680 amino acid residues that form into a single active monomer which aids in the intracellular degradation of peptides. Dcp coordinates to divalent zinc which sits in the pocket of the active site and is composed of four subsites: S1’, S1, S2, and S3, each subsite attracts certain amino acids at a specific position on the substrate enhancing the selectivity of the enzyme. The four subsites detect and bind different amino acid types on the substrate peptide in the P1 and P2 positions. Some metallic divalent cations such as Ni+2, Cu+2, and Zn+2 inhibit the function of the enzyme around 90%, whereas other cations such as Mn+2, Ca+2, Mg+2, and Co+2 have slight catalyzing properties, and increase the function by around 20%. Basic amino acids such as Arginine bind preferably at the S1 site, the S2 site sits deeper in the enzyme therefore is restricted to bind hydrophobic amino acids with phenylalanine in the P2 position. Dcp is divided into two subdomains (I, and II), which are the two sides of the clam shell-like structure and has a deep inner cavity where a pair of histidine residues bind to the catalytic zinc ion in the active site. Peptidyl-Dipeptidase Dcp is classified like Angiotensin-I converting enzyme (ACE) which is also a carboxypeptidase involved in blood pressure regulation, but due to structural differences and peptidase activity between these two enzymes they had to be examined separately. ACE has endopeptidase activity, whereas Dcp strictly has exopeptidase activity based on its cytoplasmic location and therefore their mechanisms of action are differentiated. Another difference between these enzymes is that the activity of Peptidyl-Dipeptidase Dcp is not enhanced in the presence of chloride anions, whereas chloride enhances ACE activity.

Lysyl endopeptidase is an enzyme. This enzyme catalyses the following chemical reaction

References

  1. ↑ Joseph S. Fruton (1990). Contrasts in Scientific Style: Research Groups in the Chemical and Biochemical Sciences. Vol. 191. American Philosophical Society. pp. 105–106. ISBN   0-87169-191-4.
  2. ↑ Cohnheim, 0 (1901). "Die Umwandlung des Eiweis s durch die Darmwand". Zeitschrift für Physiologische Chemie. 33 (5–6): 451–465. doi:10.1515/bchm2.1901.33.5-6.451.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  3. 1 2 Matthews DM (1978). "Otto Cohnheim--the forgotten physiologist". British Medical Journal. 2 (6137): 618–9. doi:10.1136/bmj.2.6137.618. PMC   1607550 . PMID   359089.
  4. ↑ Emil L Smith (1948). "The peptidases of skeletal, heart and uterine muscle". Journal of Biological Chemistry. 173 (2): 553–569. doi: 10.1016/S0021-9258(18)57428-7 . PMID   18910712.
  5. 1 2 3 Emil L Smith; Max Bergmann (1944). "The peptidases of intestinal mucosa" (PDF). Journal of Biological Chemistry. 153 (2): 627–651. doi: 10.1016/S0021-9258(18)72006-1 .
  6. ↑ H. M. Vernon (1904). "The universal presence of erepsin in animal tissues". J Physiol. 32 (1): 33–50. doi:10.1113/jphysiol.1904.sp001063. PMC   1465616 . PMID   16992755.
  7. ↑ Nathan Berman & Leo F. Rettger (1916). "Bacterial Nutrition: a Brief Note on the Production of Erepsin by Bacteria". Journal of Bacteriology. 1 (5): 537–539. doi:10.1128/jb.1.5.537-539.1916. PMC   378674 . PMID   16558717.
  8. ↑ HS Reed and HS Stahl (1911). "The Erepsins of Glomerella Rufomaculans and Sphaeropsis Malorum" (PDF). Journal of Biological Chemistry. 10 (2): 109–112. doi: 10.1016/S0021-9258(18)91427-4 .
  9. ↑ Emil L Smith (1949). James Murray Luck (ed.). "Proteolytic enzymes". Annual Review of Biochemistry. 18: 35. doi:10.1146/annurev.bi.18.070149.000343.
  10. ↑ James Batcheller Sumner; George Frederick Somers (1943). Chemistry and methods of enzymes. Academic Press. p. 146.
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