Elastase
I.U.B.: 3.4.21.36
Elastase, like trypsin and chymotrypsin, is a serine protease that also hydrolyses amides and esters (Brown and Wold 1973). It is produced in the pancreas as an inactive zymogen, proelastase, and activated in the duodenum by trypsin. Elastase is distinctive in that it acts upon elastin.
Because elastin in found in highest concentrations in the elastic fibers of connective tissues, elastase is frequently used to dissociate tissues which contain extensive intercellular fiber networks. For this purpose, it is usually used with other enzymes such as collagenase, trypsin, and chymotrypsin. Elastase is the enzyme of choice for the isolation of Type II cells from the lung. Additional information regarding the use of elastase in tissue dissociation can be found in the Worthington Tissue Dissociation Guide.
Elastase is also found in blood components (Legrand et al. 1975; Taylor and Crawford 1975; Tuhy and Powers 1975; Janoff and Basch 1971 and Janoff et al. 1971). According to Janoff and Scherer (1968) the serum enzyme, identical with pancreatic elastase, differs from the elastase of polymorphonuclear leukocytes. It is indicated that the leukocyte enzyme, which is inhibited by α1-antitrypsin but not by pancreatic trypsin inhibitor, mediates pathological elastolysis during acute arteritis and pulmonary emphysema. Kaplan et al. (1973) report on the induction of emphysema with elastase. See also Talamo et al. (1971). Bieth et al. (1974) indicate elastase involvement in atherosclerosis and acute hemorrhagic pancreatitis.
Elastase from Streptomyces griseus has been reported by Gertler and Trop (1971), from Flavobacterium immotum by Ozak and Shiio (1975) and from moose by Stevenson and Voordouw (1975).
Characteristics of Elastase from Porcine Pancreas:
Molecular weight: 25,900 (Shotton and Hartley 1973).
Composition: Shotton and Hartley (1973) have reported on the amino acid sequence of elastase. It is a single peptide chain of 240 residues and contains 4 disulfide bridges. Sawyer et al. (1973), Shotton and Watson et al. (1970) have reported on crystal conformation and tertiary structure. Gorbunoff and Timasheff (1972) have indicated conformational behavior shifts in the alkaline range.
Active sites studies have been reported by Atlas and Berger (1973), Thomas and Denniss (1973), and Thompson and Blout (1973). According to Bieth and Wermuth (1973), it is possible that the active center is composed of several subsites. Other active site studies have been reported by Brown and Wold (1973) and Gertler (1971).
Gertler (1971) has indicated that the elastolytic activity is due only to its electrostatic adsorption onto elastin. Jordan et al. (1974) show that the susceptibility of elastin to hydrolysis may be controlled by elastin ligands, a suggestion also made by Kagan et al. (1972) concerning a 6X enhancement of proteolysis of elastin by its prior incubation in sodium dodecyl sulfate.
In 1969, Uram and Lamy purified two elastase zymogens from porcine pancreas separated electrophoretically. Ledoux and Lamy (1975) have reported further on zymogens A and B which can be activated and which manifest different specificities as well as isoelectric points. Ardelt (1974) has also reported on a second porcine elastase obtained on DEAE-Sephadex using 3 M urea in the equilibrating buffer.
Optimum pH: 8.5.
Extinction coefficient: = 22 (Feinstein et al. 1973).
Isoelectric point: 8.5.
Specificity: The catalytic activity of elastase has been reported by: Gold and Shalitin (1975), Kasafírek et al. (1974), Thompson (1973), Atlas and Berger (1972) , Marshall and Akgun (1971), and Schellenberger et al. (1989).
Inhibitors: Elastase is inhibited by diisopropyl-phosphofluoridate and alkyl isocyanates (Brown and Wold 1971). Derivatives of dipeptides and alanine, valine, leucine and isoleucine are effective competitive inhibitors (Dzialoszynski and Hofmann 1973). Soybean trypsin inhibitor and kallikrein inhibitor suppress proteolytic but not elastolytic activity. (Walford and Kickhofen 1962), (Kasafírek et al. 1974). Elastase is inhibited by peptide chloromethyl ketone (Thompson and Blout 1973), (Powers and Tuhy 1972 and 1973). Shaw and Whitaker (1973) have also reported on inhibition of elastase.
Stability: Elastase is unstable below pH 3-4. When stored as a dry powder the enzyme is stable 6-12 months.