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pancreatic elastase
Pancreatic elastase is a form of elastase that is produced in the acinar cells of the pancreas, initially produced as an inactive zymogen and later activated in the duodenum by trypsin. Elastases form a subfamily of serine proteases, characterized by a distinctive structure consisting of two beta barrel domains converging at the active site that hydrolyze amides and esters amongst many proteins in addition to elastin, a type of connective tissue that holds organs together. Pancreatic elastase 1 is a serine endopeptidase, a specific type of protease that has the amino acid serine at its active site. Although the recommended name is pancreatic elastase, it can also be referred to as elastase-1, pancreatopeptidase, PE, or serine elastase.
The first isozyme, pancreatic elastase 1, was initially thought to be expressed in the pancreas. However it was later discovered that it was the only chymotrypsin-like elastase that was not expressed in the pancreas. In fact, pancreatic elastase is expressed in basal layers of epidermis (at protein level). Hence pancreatic elastase 1 has been renamed elastase 1 (ELA1) or chymotrypsin-like elastase family, member 1 (CELA1).〔 For a period of time, it was thought that that ELA1 / CELA1 was not transcribed into a protein. However it was later discovered that it was expressed in skin keratinocytes.
Clinical literature that describes human elastase 1 activity in the pancreas or fecal material is actually referring to chymotrypsin-like elastase family, member 3B (CELA3B).
== Structure ==
Pancreatic elastase is a compact globular protein with a hydrophobic core. This enzyme is formed by three subunits. Each subunit binds one calcium ion (cofactor). There are three important metal-binding sites in amino acids 77, 82, 87. The catalytic triad , located in the active site is formed by three hydrogen-bonded amino acid residues (H71, D119, S214), and plays an essential role in the cleaving ability of all proteases. It is composed of a single peptide chain of 240 amino acids and contains 4 disulfide bridges. It has a high degree of sequence identity with pancreatic elastases that correspond to other species, such as the rat's, with whom it shares 86% of its sequence.〔(【引用サイトリンク】 Elastase )〕 Its enzymatic activity is a result of the specific three-dimensional conformation which its single polypeptide chain adopts, and therefore, activity is lost by denaturation and/or conformational changes.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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