Proteolysis is the directed degradation (digestion) of proteins by cellular enzymes called proteases or by intramolecular digestion. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Peptidases (proteases [pronounced pro-tea-aces] and proteolytic enzymes are also commonly used) are enzymes which break peptide bonds of proteins. ...

Proteolysis is used by the cell for several purposes. They include

• Removal of N-terminal methionine residues after translation.
• Removal of the signal sequence of peptides after their transport through a membrane
• Separation of viral proteins that were translated from a monocistronic mRNA
• Digestion of proteins from foods as a source of amino acids
• Conversion of predecessor-proteins (proenzymes, zymogens, prehormones) into their final structures.

Examples of proteases are trypsin and chymotrypsin. The N-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free amine group (NH2). ... Methionine (Met, M. C5H11NO2S) is a essential nonpolar amino acid, and a lipotropic. ... Translation in the cytoplasm; tRNA carries amino acids which are added to the growing peptide chain in the ribosome. ... The term signal sequence can refer to any of the following: protein targeting signal peptide This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... This article or section should include material from Net flux A membrane is a thin, typically planar structure or material that separates two environments. ... A common alternate meaning of virus is computer virus. ... Monocistronic is an adjective used in genetics which usually refers to messenger RNA (mRNA) and means that a single polypeptide chain will result from its translation. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... A zymogen is an inactive enzyme pre-cursor. ... Trypsin is a digestive enzyme that cleaves peptide bonds only at carboxyl side of lysine and arginine residiues. ... Chymotrypsin Chymotrypsin (bovine γ chymotrypsin: PDB 1AB9, EC 3. ...