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Proteolysis
 
 
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Proteolysis is the directed degradation (digestion) of protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s by cellular enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s called protease
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, which form a molecule of protein....
s or by intramolecular digestion.

eolysis is used by the cell for several purposes. They include:

Proteolysis is also used in research and diagnostic applications:

ples of serine proteases include:

ain venoms, such as those produced by venomous snake
Snake

Snakes are elongate legless carnivore reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears....
s, can also cause proteolysis.






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Proteolysis is the directed degradation (digestion) of protein
Protein

Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
s by cellular enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
s called protease
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, which form a molecule of protein....
s or by intramolecular digestion.

Purposes

Proteolysis is used by the cell for several purposes. They include:
  • Removal of N-terminal methionine
    Methionine

    Methionine is an a-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This Essential amino acid is classified as nonpolar....
     residues after translation.
  • Removal of the signal sequence
    Signal peptide

    A signal peptide is a short peptide chain that directs the post-translation transport of a protein.Signal peptides may also be called targeting signals, signal sequences, transit peptides, or localization signals....
     of peptides after their transport through a membrane
    Cell membrane

    The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
  • Separation of viral proteins that were translated from a polycistronic mRNA
  • Digestion of proteins from foods as a source of amino acid
    Amino acid

    In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
    s
  • Conversion of predecessor-proteins (proenzymes, zymogen
    Zymogen

    A zymogen is an inactive enzyme Protein precursor. A zymogen requires a biochemical change for it to become an active enzyme. The biochemical change usually occurs in a lysosome where a specific part of the precursor enzyme is cleaved in order to activate it....
    s, prehormone
    Prehormone

    A prehormone is a biochemical substance secreted by glandular tissue and has minimal or no significant biological activity, but it is converted in peripheral tissues into an active hormone....
    s) into their final structures.
  • Degradation of cyclins at different stages of the cell cycle
    Cell cycle

    The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission....
    .


Proteolysis is also used in research and diagnostic applications:
  • In-gel digestion
    In-gel digestion

    The in-gel digestion is part of the sample preparation for the mass spectrometry identification of proteins in course of Proteomics. The method was introduced 1992 by Rosenfeld....
     of proteins after separation by gel electrophoresis
    Gel electrophoresis

    Gel electrophoresis is a technique used for the separation of DNA , RNA , or protein molecules using an electric current applied to a gel matrix....
     for the identification by mass spectrometry
    Mass spectrometry

    Mass spectrometry is an analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds....
    .
  • Digestion of proteins in solution for proteome analysis
    Proteomics

    Proteomics is the large-scale study of proteins, particularly their protein structure and functional genomics. Proteins are vital parts of living organisms, as they are the main components of the physiological metabolic pathways of biological cell....
     by LC-MS.


Examples

Examples of serine proteases include:
  • trypsin
    Trypsin

    Trypsin is a serine protease found in the digestive system, where it breaks down proteins. Trypsin predominantly cleaves peptide chains at the carboxyl side of the amino acids lysine and arginine, except when either is followed by proline....
  • chymotrypsin
    Chymotrypsin

    Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin cleaves peptides at the carboxyl side of tyrosine, tryptophan, and phenylalanine because these three amino acids contain aromatic rings, which fit into a 'hydrophobic pocket' in the enzyme....
  • elastase
    Elastase

    In molecular biology, elastase is an enzyme from the class of proteases , that break down proteins....


Venoms

Certain venoms, such as those produced by venomous snake
Snake

Snakes are elongate legless carnivore reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears....
s, can also cause proteolysis. These venoms are, in fact, complex digestive fluids that begin their work outside of the body. Proteolytic venoms cause a wide range of toxic effects, including effects that are:
  • cytotoxic (cell-destroying)
  • hemotoxic
    Hemotoxin

    Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells , disrupt blood thrombus, and/or cause Organ degeneration and generalized Biological tissue damage....
     (blood-destroying)
  • myotoxic
    Myotoxin

    Myotoxins are small, basic peptides found in snake Venom s, such as in that of certain rattlesnakes. This involves a non-enzymatic mechanism that leads to severe muscle necrosis....
     (muscle-destroying)
  • hemorrhagic (bleeding)


See also

  • The Proteolysis Map
    The Proteolysis Map

    The Proteolysis MAP is an integrated web resource focused on proteases....
  • Proteasome
    Proteasome

    Proteasomes are large protein complexes inside all eukaryotes and archaea, as well as in some bacteria. In eukaryotes, they are located in the cell nucleus and the cytoplasm....
  • In-gel digestion
    In-gel digestion

    The in-gel digestion is part of the sample preparation for the mass spectrometry identification of proteins in course of Proteomics. The method was introduced 1992 by Rosenfeld....


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