Proteolytic enzymes

About: Proteolytic enzymes is a research topic. Over the lifetime, 23096 publications have been published within this topic receiving 835544 citations.

Distribution of cathepsins B and H in rat tissues and peripheral blood cells.

Abstract: The concentrations of cathepsins B and H in various tissues and peripheral blood cells of rats were determined by means of sensitive immunoassays. The minimum detectable amounts of cathepsins B and H were 30 pg and 20 pg/assay, respectively, and the presence of endogenous thiol proteinase inhibitors did not interfere with the immunoassays. Cathepsin B was found at high levels in the kidney, vagina, spleen, and adrenal gland, and cathepsin H at high levels in the kidney, vagina, liver, lung, and spleen. Low levels of cathepsins B and H were present in the heart, skeletal muscle, and testis. The ratios of cathepsins B and H in various organs were different: the brain and adrenal gland contained much higher levels of cathepsin B than of cathepsin H, whereas the lung and liver contained higher levels of cathepsin H than of cathepsin B. In several organs such as the kidney, spleen, liver, and lungs, the level of cathepsins B plus H was much higher than that of thiol proteinase inhibitors (TPI-alpha + TPI-beta), whereas in tissues containing large amounts of TPI-alpha, such as the skin, esophagus and stomach, the level of inhibitors was higher than that of cathepsins B plus H. Of the peripheral blood cells tested, macrophages had the highest contents of cathepsins B and H, and so their level of cathepsins B plus H was much higher than that of TPI-alpha plus TPI-beta, whereas lymphocytes and neutrophils contained comparable amounts of proteinases and inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Degradation of the epidermal-dermal junction by proteolytic enzymes from human skin and human polymorphonuclear leukocytes

Abstract: The degradation of normal human skin by the human polymorphonuclear leukocyte proteinases cathepsin G and elastase, and by a human skin chymotrypsin-like proteinase that appears to be a mast cell constituent, was examined. Enzymes were incubated with fresh, split-thickness skin for up to 8 h; the tissue was examined ultrastructurally and immunohistochemically using antibodies to known basement membrane constituents. In all cases, the primary damage observed was at the epidermal-dermal junction. Elastase degraded the lamina densa leaving scattered and disorganized anchoring fibrils, dermal microfibril bundles, and normal-appearing collagen fibers. Immunohistochemically, type IV collagen, laminin, KF1 antigen, and EBA antigen were absent. The bullous pemphigoid antigen was present and localized on the basal cells. Epidermal-dermal separation produced by the chymotrypsin-like proteinases, cathepsin G, and the human skin proteinase, was confined to the lamina lucida. The lamina densa and sub-lamina densa fibrillar network remained intact. The human skin chymotrypsin-like proteinase produced extensive epidermal-dermal separation, while cathepsin G, at comparable concentrations, produced only focal separations. Immunohistochemically, all antigens were present after incubation with enzyme. The bullous pemphigoid antigen, however, was found on the epidermal side of the split, while laminin was found on the dermal side. These results show that the epidermal-dermal junction is highly susceptible to neutral serine proteinases located in mast cells and polymorphonuclear leukocytes. Although all the proteinases produce epidermal-dermal separation, the patterns and extent of degradation are different. The distinctive patterns of degradation may provide a clue to the involvement of these proteinases in skin diseases.

Nascent prehormones are intermediates in the biosynthesis of authentic bovine pituitary growth hormone and prolactin

Abstract: Major translation products of bovine pituitary RNA in a wheat germ cell-free system were identified as larger forms (prehormones) of growth hormone and prolactin containing amino-terminal extensions of 26 or 27 and 30 amino acid residues, respectively. However, translation of bovine pituitary RNA in the wheat germ cell-free system in the presence of microsomal membranes prepared from canine pancreas or bovine pituitary yielded products that were of the same size as authentic growth hormone and prolactin; by partial amino-terminal sequence analysis they were shown to contain the correct unique amino-terminal sequence of prolactin and the two correct amino termini of authentic growth hormone; moreover, they were found to be segregated within the microsomal vesicles in that they were largely inaccessible to degradation by proteolytic enzymes. When microsomal membranes were present after rather than during translation, prehormones were neither cleaved nor segregated. These results strongly suggest that the synthesis and segregation of the authentic hormone observed in the presence of membranes proceeds via a nascent prehormone rather than a completed prehormone.

Cysteine Proteases: Modes of Activation and Future Prospects as Pharmacological Targets.

Abstract: Proteolytic enzymes are crucial for a variety of biological processes in organisms ranging from lower (virus, bacteria, and parasite) to the higher organisms (mammals). Proteases cleave proteins into smaller fragments by catalyzing peptide bonds hydrolysis. Proteases are classified according to their catalytic site, and distributed into four major classes: cysteine proteases, serine proteases, aspartic proteases, and metalloproteases. This review will cover only cysteine proteases, papain family enzymes which are involved in multiple functions such as extracellular matrix turnover, antigen presentation, processing events, digestion, immune invasion, hemoglobin hydrolysis, parasite invasion, parasite egress, and processing surface proteins. Therefore, they are promising drug targets for various diseases. For preventing unwanted digestion, cysteine proteases are synthesized as zymogens, and contain a prodomain (regulatory) and a mature domain (catalytic). The prodomain acts as an endogenous inhibitor of the mature enzyme. For activation of the mature enzyme, removal of the prodomain is necessary and achieved by different modes. The pro-mature domain interaction can be categorized as protein–protein interactions (PPIs) and may be targeted in a range of diseases. Cysteine protease inhibitors are available that can block the active site but no such inhibitor available yet that can be targeted to block the pro-mature domain interactions and prevent it activation. This review specifically highlights the modes of activation (processing) of papain family enzymes, which involve auto-activation, trans-activation and also clarifies the future aspects of targeting PPIs to prevent the activation of cysteine proteases.

Neutrophil elastase: mediator of extracellular matrix destruction and accumulation.

Abstract: Of the myriad proteolytic enzymes implicated in the development of lung disease, neutrophil elastase has undoubtedly some of the most versatile effects. Although its key physiologic role is in innate host defense, it can also participate in tissue remodeling and possesses secretagogue actions that are now recognized as important to local inflammatory responses. Although unopposed neutrophil elastase activity has been implicated in the development of emphysema for several decades, only relatively recently has a pathogenetic function been ascribed to this serine proteinase in situations where excessive extracellular matrix deposition occurs. The use of genetically manipulated animal models is starting to uncover the potential ways in which its actions might influence fibrotic lung repair. Emerging evidence suggests that the engagement of cellular pathways with more direct effects on fibrogenic mediator generation and collagen synthesis appears to underpin the actions of neutrophil elastase in promoting lung matrix accumulation.