Endopeptidase
Encyclopedia
Endopeptidase or endoproteinase are proteolytic
peptidases that break peptide bonds of nonterminal amino acid
s (i.e. within the molecule), in contrast to exopeptidase
s, which break peptide bonds from their end-pieces. For this reason, endopeptidases cannot break down peptides into monomers, while exopeptidases can break down proteins into monomers. A particular case of endopeptidase is the oligopeptidase
, whose substrates are oligopeptides instead of proteins.
They are usually very specific for certain amino acids. Examples of endopeptidases include:
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
peptidases that break peptide bonds of nonterminal 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...
s (i.e. within the molecule), in contrast to exopeptidase
Exopeptidase
An exopeptidase is an enzyme produced in the pancreas that catalyses the removal of an amino acid from the end of a polypeptide chain. Exopeptidase cleaves the end of a polypeptide chain....
s, which break peptide bonds from their end-pieces. For this reason, endopeptidases cannot break down peptides into monomers, while exopeptidases can break down proteins into monomers. A particular case of endopeptidase is the oligopeptidase
Oligopeptidase
Oligopeptidase is an enzyme that cleaves peptides but not proteins, a property that is due to its structure: the active site of this enzyme is located at the end of a narrow cavity which can only be reached by peptides...
, whose substrates are oligopeptides instead of proteins.
They are usually very specific for certain amino acids. Examples of endopeptidases include:
- TrypsinTrypsinTrypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
- cuts after Arg or Lys, unless followed by Pro. Very strict. Works best at pH 8. - ChymotrypsinChymotrypsinChymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...
- cuts after Phe, Trp, or Tyr, unless followed by Pro. Cuts more slowly after Asn, His, Met or Leu. Works best at pH 8. - ElastaseElastaseIn molecular biology, elastase is an enzyme from the class of proteases that break down proteins.- Forms and classification:There exist eight human genes for elastase:Bacterial forms: Organisms such as P...
- cuts after Ala, Gly, Ser, or Val, unless followed by Pro. - ThermolysinThermolysinThermolysin is a thermostable neutral metalloproteinase enzyme produced by the gram-positive bacteria Bacillus thermoproteolyticus. It requires one zinc ion for enzyme activity and four calcium ions for structural stability. Thermolysin specifically catalyzes the hydrolysis of peptide bonds...
- cuts before Ile, Met, Phe, Trp, Tyr, or Val, unless preceded by Pro. Sometimes cuts after Ala, Asp, His or Thr. Heat stable. - PepsinPepsinPepsin is an enzyme whose precursor form is released by the chief cells in the stomach and that degrades food proteins into peptides. It was discovered in 1836 by Theodor Schwann who also coined its name from the Greek word pepsis, meaning digestion...
- cuts before Leu, Phe, Trp or Tyr, unless preceded by Pro. Also others, quite nonspecific; works best at pH 2. - Endopeptidase V8 (alias Glu-C) - cuts after Glu. Works best at pH 8.