Aminopeptidases are
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s that
catalyze
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
the cleavage of
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
s from the amino terminus (
N-terminus) of
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s or
peptide
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
...
s (exopeptidases). They are widely distributed throughout the animal and plant kingdoms and are found in many subcellular
organelles, in
cytosol
The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...
, and as
membrane
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...
components. Aminopeptidases are used in essential cellular functions. Many, but not all, of these peptidases are zinc
metalloenzymes.
Some aminopeptidases are
monomeric
In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
Mo ...
, and others are assemblies of relatively high mass (50 kDa) subunits.
cDNA sequences are available for several aminopeptidases and a
crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns ...
of the open state of human endoplasmic reticulum Aminopeptidase 1
ERAP1 is presented here.
[ Amino acid sequences determined directly or deduced from cDNAs indicate some amino acid sequence homologies in organisms as diverse as '']Escherichia coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...
'' and mammals, particularly in catalytically important residues or in residues involved in metal ion binding.[
One important aminopeptidase is a ]zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
-dependent enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
produced and secreted by glands of the small intestine. It helps the enzymatic digestion of proteins. Additional digestive enzymes produced by these glands include dipeptidases, maltase
Maltase (, ''alpha-glucosidase'', ''glucoinvertase'', ''glucosidosucrase'', ''maltase-glucoamylase'', ''alpha-glucopyranosidase'', ''glucosidoinvertase'', ''alpha-D-glucosidase'', ''alpha-glucoside hydrolase'', ''alpha-1,4-glucosidase'', ''alp ...
, sucrase, lactase
Lactase is an enzyme produced by many organisms. It is located in the brush border of the small intestine of humans and other mammals. Lactase is essential to the complete digestion of whole milk; it breaks down lactose, a sugar which gives ...
, and enterokinase.
See also
* Alanine aminopeptidase
* Carboxypeptidase
References
External links
*
Zinc proteins
EC 3.4
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