Elastase


In molecular biology, elastase is an enzyme from the class of proteases that break down proteins. In particular, it is a serine protease.

Forms and classification

Eight human genes exist for elastase:
FamilyGene symbolGene symbolProtein nameProtein nameEC number
FamilyApprovedPreviousApprovedPreviousEC number
chymotrypsin-
like		CELA1ELA1chymotrypsin-like elastase family, member 1elastase 1, pancreatic
chymotrypsin-
like		CELA2AELA2Achymotrypsin-like elastase family, member 2Aelastase 2A, pancreatic
chymotrypsin-
like		CELA2BELA2Bchymotrypsin-like elastase family, member 2Belastase 2B, pancreatic
chymotrypsin-
like		CELA3AELA3Achymotrypsin-like elastase family, member 3Aelastase 3A, pancreatic
chymotrypsin-
like		CELA3BELA3Bchymotrypsin-like elastase family, member 3Belastase 3B, pancreatic
chymotrypsinCTRCELA4chymotrypsin C elastase 4
neutrophilELANEELA2neutrophil elastaseelastase 2
macrophageMMP12HMEmacrophage metalloelastasemacrophage elastase

Some bacteria also produce elastase. In bacteria, elastase is considered a virulence factor.

Function

Elastase breaks down elastin, an elastic fibre that, together with collagen, determines the mechanical properties of connective tissue. The neutrophil form breaks down the Outer membrane protein A of E. coli and other Gram-negative bacteria. Elastase also has the important immunological role of breaking down Shigella virulence factors. This is accomplished through the cleavage of peptide bonds in the target proteins. The specific peptide bonds cleaved are those on the carboxyl side of small, hydrophobic amino acids such as glycine, alanine, and valine. For more on how this is accomplished, see serine protease.

The role of human elastase in disease

A1AT

Elastase is inhibited by the acute-phase protein α1-antitrypsin, which binds almost irreversibly to the active site of elastase and trypsin. A1AT is normally secreted by the liver cells into the serum. Alpha-1 antitrypsin deficiency leads to uninhibited destruction of elastic fibre by elastase; the main result is emphysema.

Cyclic neutropenia

The rare disease cyclic neutropenia is an autosomal dominant genetic disorder characterised by fluctuating neutrophil granulocyte counts over 21-day periods. During neutropenia, patients are at risk for infections. In 1999, this disease was linked to disorders in the ELA-2 / ELANE gene. Other forms of congenital neutropenia also appear to be linked to ELA-2 mutations.

Other diseases

Neutrophil elastase is responsible for the blistering in bullous pemphigoid, a skin condition, in the presence of antibodies.

The role of bacterial elastase in disease

Elastase has been shown to disrupt tight junctions, cause proteolytic damage to tissue, break down cytokines and alpha proteinase inhibitor, cleave immunoglobulin A and G, and cleave both C3bi, a component of the complement system, and CR1, a receptor on neutrophils for another complement molecule involved in phagocytosis. The cleavage of IgA, IgG, C3bi, and CR1 contributes to a decrease of the ability of neutrophils to kill bacteria by phagocytosis. Together, all these factors contribute to human pathology.