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.
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.
A carboxypeptidase 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 bonds at the N-terminus of proteins. Humans, animals, bacteria and plants contain several types of carboxypeptidases that have diverse functions ranging from catabolism to protein maturation. At least two mechanisms have been discussed.
Dipeptidyl peptidase-4, also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene. DPP4 is related to FAP, DPP8, and DPP9. The enzyme was discovered in 1966 by Hopsu-Havu and Glenner, and as a result of various studies on chemism, was called dipeptidyl peptidase IV [DP IV].
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."
A metalloexopeptidase is a type of enzyme that acts as a metalloproteinase exopeptidase. These enzymes have a catalytic mechanism involving a metal, often zinc. They function in molecular biology as agents that cut the terminal peptide bonds ending peptide chains. Analogous to slicing the end off a loaf of bread, the process releases a single amino acid for use.
Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism.
Prolidase deficiency (PD) is an extremely uncommon autosomal recessive disorder associated with collagen metabolism that affects connective tissues and thus a diverse array of organ systems more broadly, though it is extremely inconsistent in its expression.
Carboxypeptidase E (CPE), also known as carboxypeptidase H (CPH) and enkephalin convertase, is an enzyme that in humans is encoded by the CPE gene. This enzyme catalyzes the release of C-terminal arginine or lysine residues from polypeptides.
Carboxypeptidase A usually refers to the pancreatic exopeptidase that hydrolyzes peptide bonds of C-terminal residues with aromatic or aliphatic side-chains. Most scientists in the field now refer to this enzyme as CPA1, and to a related pancreatic carboxypeptidase as CPA2.
The discovery of an orally inactive peptide from snake venom established the important role of angiotensin converting enzyme (ACE) inhibitors in regulating blood pressure. This led to the development of captopril, the first ACE inhibitor. When the adverse effects of captopril became apparent new derivates were designed. Then after the discovery of two active sites of ACE: N-domain and C-domain, the development of domain-specific ACE inhibitors began.
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.
Carboxypeptidase N catalytic chain is an enzyme that in humans is encoded by the CPN1 gene.
Chromosome 9 open reading frame 3 (C9ORF3) also known as aminopeptidase O (APO) is an enzyme which in humans is encoded by the C9ORF3 gene. The protein encoded by this gene is an aminopeptidase which is most closely related in sequence to leukotriene A4 hydrolase (LTA4H). APO is a member of the M1 metalloproteinase family.
Beta-peptidyl aminopeptidase is an enzyme. This enzyme catalyses the following chemical reaction:
Dipeptidyl-peptidase II is an enzyme. This enzyme catalyses the following chemical reaction:
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.
Lysine carboxypeptidase is an enzyme. This enzyme catalyses the following chemical reaction:
An endopeptidase inhibitor is a drug that inhibits one or more endopeptidase enzymes. Endopeptidases are one of two types of proteases, the other being exopeptidases. Endopeptidases cleave peptide bonds of non-terminal amino acids, whereas exopeptidases break terminal bonds, resulting in the release of a single amino acid or dipeptide from the peptide chain.
An exopeptidase inhibitor is a drug that inhibits one or more exopeptidase enzymes. Exopeptidases are one of two types of proteases, the other being endopeptidases. Exopeptidases cleave peptide bonds of terminal amino acids, resulting in the release of a single amino acid or dipeptide from the peptide chain, whereas endoeptidases break non-terminal bonds.
