Cathepsin E (EC 3.4.23.34)--a review

Cathepsin E belongs to the third class of enzymes - hydrolases, a subclass of peptide bond hydrolases and a sub-subclass of endopeptidases with aspartic catalytic sites. Cathepsin E is an endopeptidase with substrate specificity similar to that of cathepsin D. In a human organism, cathepsin E occurs in: erythrocytes, thymus, dendritic cells, epithelial M cells, microglia cells, Langerhans cells, lymphocytes, epithelium of gastrointestinal tract, urinary bladder, lungs, osteoclasts, spleen and lymphatic nodes. In human cells, loci of the gene of pre-procathepsin E are located on chromosome 1 in the region 1231-32. The catalytic site of cathepsin E is two residues of aspartic acid - Asp96 and Asn281, occurring in amino acid triads with sequences DTG96-98 and DTG281-283. To date, no particular role of cathepsin E in the metabolism of proteins in normal tissues has been found. However, it is known that there are many documented pathological conditions in which overexpression of cathepsin E occurs.

Cathepsin A activity of a parietal thrombus of an abdominal aortic aneurysm

We evaluated the cathepsin A activity of a parietal thrombus of an abdominal aortic aneurysm. We compared this activity to that of a retracted blood clot homogenate. Cathepsin A of aneurysm parietal thrombus homogenate and blood clot homogenate showed the highest activity on Z-Phe-Ala. It was lower on Z-Phe-Phe, Z-Glu-Tyr, Z-Glu-Phe, Z-Gly-Phe, and the lowest activity was on Z-Gly-Ala. We conclude that cathepsin A's activity on a parietal thrombus of an aneurysm is much higher than blood clot cathepsin A activity.

Activity of coagulation and fibrinolytic system components in the vein thrombus

PURPOSE

Behaviour of the vein thrombus is determined by the activity ratio of coagulation factors to factors of fibrinolytic system. The aim of the study is to evaluate activity of some coagulation and fibrinolytic factors in the vein thrombus.

MATERIAL AND METHODS

The activity of platelets aggregating factors, tissue factor, thrombin, antithrombins, antiheparin factors, plasminogen activators, plasmin (plasminogen) and antiplasmins of the vein thrombus homogenate was determined using coagulative, fibrinolytic and caseinolytic tests. Retracted blood clot was a compared material.

RESULTS

Tissue factor activity in the vein thrombus was above twofold higher and antiheparin activity was nearly twice higher in comparison to the blood clot. The vein thrombus contains also active thrombin. Plasminogen activators activity in the vein thrombus was twofold higher and activity of plasmin (plasminogen) was threefold higher than in the blood clot. High activity of the tissue factor, substances neutralizing heparin and presence of thrombin intensify the thrombus enlargement. However, the thrombotic tendency may be balanced by a high activity of plasminogen activators and high activity of plasmin (plasminogen).

CONCLUSIONS

1) Vein thrombus is characterized by high activity of tissue factor, presence of active thrombin and high antiheparin activity. 2) High coagulative potential of vein thrombus is balanced to a certain grade by high fibrinolytic potential: high activity of plasminogen activators and high activity of plasmin (plasminogen), as well as absence of antiplasmins activity.

[Concentration and activity of cathepsin D in the blood plasma and serum of patients with abdominal aortic aneurysm]

Concentration and activity of cathepsin D are markedly higher in the blood plasma of patients with abdominal aortic aneurysm than in the blood plasma of healthy subjects. The difference results from release of big amounts of procathepsin D and increased release of the active enzyme into circulating blood of patients with aortic aneurysm. Concentration and activity of cathepsin D in the blood serum of patients with aortic aneurysm are also higher than in the serum of healthy subjects. Concentration and activity of cathepsin D are markedly higher in the blood serum of patients with aortic aneurysm and in healthy subjects as compared to the blood plasma. The difference is due to the release of marked amounts of procathepsin D and cathepsin D from morphotic elements in vitro during blood coagulation and clot retraction.

[Antiheparin activity of the aneurysm wall and parietal thrombus and blood plasma of patients with aortic aneurysm]

Aneurysm dilatation is filled by parietal thrombus. Its magnitude is determined by the ratio of coagulative to anticoagulative activities above all. The aim of the study was to assess antiheparin activity, contents of heparin neutralizing chemical compounds and glycosaminoglycans with anticoagulative activity as well in the aneurysm wall, parietal thrombus filling the aneurysm dilatation and blood plasma/blood serum of patients with aortic aneurysm. The studied material consisted of aneurysm walls and parietal thrombi extracts, as well as of blood plasma/serum of patients with aortic aneurysm. Extracts of normal aorta from organ donors and blood plasma/serum of healthy subjects were the control material. Antiheparin and antithrombin III activities, as well as contents of heparin neutralizing compounds and heparin-like acting glycosaminoglycans were evaluated in the investigated material with chemical methods. The aneurysm wall, parietal thrombus filling the aneurysm dilatation and blood plasma of patients with aortic aneurysm show high antiheparin activity and increased content of heparin neutralizing compounds. However differences in glycosaminoglycans content were not demonstrated. That can predispose to formation and enlargement of parietal thrombus in aneurysm dilatation.

Activity of enzymes with different subcellular localization in the blood plasma of patients with aortic aneurysm

BACKGROUND

The wall of an abdominal aorta aneurysm shows increased activity of metalloproteinases, aspartyl cathepsins and cystein cathepsins, and decreased activity of inhibitors of these enzymes, as compared to the wall of a normal aorta. Parietal thrombi of the aneurysm also show marked proteolytic activity. The aim of our study was to determine the activity of secretory enzymes, membrane enzymes, cytosol enzymes, mitochondrial enzymes and lysosomal enzymes in the blood plasma of patients with abdominal aortic aneurysm.

MATERIAL/METHODS

Blood for examinations was collected from 15 patients with abdominal aorta aneurysm without coexisting diseases, and from the same number of healthy subjects, to determine the activity of lactic acid dehydrogenase (LDH), 5' nucleotidase (5'NT), gamma-glutamyltranspeptidase (GGTP) and cholinesterase (ChE), alanine aminotransferase (ALT), aspartic aminotransferase (AST), cathepsin B (CB), cathepsin D (CD), and cathepsin L (CL).

RESULTS

The plasma activity of ALT, AST and GGTP in the blood of patients with aortic aneurysm is lower than in the plasma of healthy subjects. The activity of LDH, 5'NT and ChE, CB and CL does not significantly differ in the plasma of patients with aortic aneurysm compared to the plasma of healthy subjects. The activity of CD is increased in the plasma of patients with aortic aneurysm.

CONCLUSIONS

Determination of cathepsin D activity may be helpful in the diagnosis of aortic aneurysm.

[Lysosomal carboxypeptidase A]

Lysosomal carboxypeptidase A (cathepsin A) is synthetized in the form of preproenzyme, which undergoes to active enzyme as a result of post-translational modification. It splits off C-terminal amino acid residues from peptides and proteins and synergizes with other proteases in degradation of cellular proteins in lysosomes. Lysosomal carboxypeptidase A has an effect on peptide hormones and peptides of biological activity of tissues and body fluids as well. It forms complexes with some glycosidases that protects them against proteolytic degradation. Deficiency of this enzyme induces storage diseases. Lysosomal carboxypeptidase A as multifunctional enzyme plays an important regulatory role in organismal metabolism.

Haemoglobin of varicose vein, varicose vein with thrombophlebitis and in parietal thrombus of varicose vein

Saphenous veins were taken for examination: unchanged, varicose with thrombophlebitis and varicose thrombus. The contents of haemoglobin and protein were determined in the homogenate of that material. Only small quantities of haemoglobin were found in walls of unchanged veins. Greater amounts of haemoglobin were observed in walls of varicose veins, especially in walls of varicose veins with thrombophlebitis. The varicose vein thrombus also contained marked quantities of haemoglobin.

Chemical compound content and enzyme activity in supernatant and sediment of liver homogenate

Evaluation was performed of chemical compound contents and enzyme activities in the whole homogenate, its supernatant and sediment. Six rabbit livers were pulverized in liquid nitrogen and homogenized. After centrifugation, the contents of protein, haemoglobin, vitamin A, vitamin E, vitamin C, as well as the activities of cathepsin B, cathepsin D, superoxide dismutase, catalase, glutathione peroxidase and reductase were assessed in the whole homogenate, its supernatant and sediment. Protein, vitamin A, superoxide dismutase, catalase, cathepsin D, glutathione peroxidase and reductase reveal uniform localisation. Vitamin C and cathepsin B are localized in supernatant, whereas haemoglobin is localized mainly in sediment. Evaluation of chemical compounds and enzyme activities should be performed in the whole homogenate, supernatant and sediment to obtain a real interpretation of biochemical disturbances in the investigated material.

Some components of oxidative-antioxidative system in human blood plasma and serum

Comparison of the concentrations and activities of components in the oxidative-antioxidative system between blood plasma and serum. Blood plasma and serum samples were obtained from 38 healthy adults to evaluate malondialdehyde concentration, the total antioxidative capacity, superoxide dismutase activity, protein and non-protein sulphydryl groups, ascorbate, haemoglobin, methaemoglobin and protein. Blood plasma shows higher activity of superoxide dismutase, as well as higher concentrations of low-molecular sulphydryl groups and ascorbate, when compared to those in blood serum. The total plasma antioxidative capacity is also higher than that assessed in blood serum. Processes of blood coagulation and blood clot retraction lead to antioxidant consumption. The evaluation of oxidative-antioxidative system for diagnostic purposes should be performed in blood plasma.

[Proteases of neutrophilic granulocytes]

The literature referring to proteolytic enzymes of neutrophilic granulocytes was surveyed. Biosynthesis, subcellular distribution, division according to the catalytic site structure, inhibitors and methods used to determine the activity of these enzymes were discussed. The survey included metaloproteases (granulocytic collagenase, gelatinase B), serine proteases (granulocytic elastase, cathepsin G, protease 3), membraneous proteases (aminopeptidase N, aminopeptidase P, neprilisine), cysteine and aspartic cathepsins. The role of these proteases in the pathology and diagnostics of certain diseases was considered.

Coagulative and fibrinolytic activity in parietal thrombus of aortic aneurysm

Lumen of aortic aneurysm is usually filled with parietal thrombus. Behaviour of the parietal thrombus is determined by the ratio of coagulation factors to factors of fibrinolytic system. Activity of some factors of coagulation and fibrinolysis in the parietal thrombus of aortic aneurysm was determined using coagulative, fibrinolytic and caseinolytic tests. Retracted, blood clot was a comparative material. Tissue factor activity in the parietal thrombus of the aneurysm was above threefold higher and antiheparin activity was nearly twice higher in comparison to the blood clot. Activity of plasminogen activators in the parietal thrombus was higher than in the blood clot. The parietal thrombus contained fourfold more of the plasminogen. Antiplasmin activity in the thrombus was above twofold lower than in the blood clot. High activity of the tissue factor and substances neutralizing heparin may intensify the thrombus growth. Yet the thrombotic tendency may be balanced by a high activity of plasminogen activators and plasminogen.

Lysosomal cysteine proteinases and their significance in pathology

The lysosomal cysteine proteinases are synthesized in a form of pre-proenzymes. They are submitted to posttranslational glycosylation and phosphorylation. These modifications make possible transport the modified proteins into Golgi apparatus and into lysosomes. Some disturbances of transport which occur mainly in tumour cells result in an increase of these enzymes activities in cytosol and in intercellular compartment. The activity of cysteine proteinases is regulated by specific inhibitors (cystatin, kininogen) which exist in some tissues and body fluids. The evaluation of activity and concentration of proteinases and inhibitors is important in clinical diagnostics.

Biological and diagnostic role of cathepsin D

Biosynthesis, posttranslating modifications, intracellular transport and activation of procathepsin D are discussed. Active cathepsin D evokes degradation of cellular and extracellular proteins and it also activates proenzymes, prohormones and growth factors and inactivates their active forms. Impairment of lysosomes in hypoxia or necrosis evokes transition of cathepsin D to cytosol and body fluids. Increase of cathepsin D content in cytosol also evokes enhancement of the synthesis rate observed among others, in neoplastic tissues and regenerating organs. Increase of cathepsin D content and activity in cytosol and blood serum is of essential diagnostic and prognostic importance in some pathologic conditions.

Activity of enzymes of various subcellular localisation in cytosol obtained after cell organelle precipitation at pH 5.0

Acidification to pH 5.0 of various organ homogenates prepared in 0.25 M sucrose causes aggregation of cell organelles. Aggregated organelles are removed through standard centrifugation. Cytosol obtained reveals only slight activity of membrane and lysosomal enzymes. The cytosol is useful for evaluation of changes in enzyme distribution in cell.

Cathepsin D activity and protein degradation products in organs and blood during experimental declamping shock

Aortic cross-clamping in dogs for 60 min causes an increase in cathepsin D activity in the kidney, liver, lung, heart, skeletal muscle and the blood serum. It causes no changes in the content of protein and its degradation products of the examined organs, apart from the lungs, where the above parameters are higher. The intensity of the observed changes in the kidney and other organs does not depend on the level of aortic cross-clamping (above or below renal arteries).

Activity of membrane, cytosol and lysosome enzymes in organs and blood serum during declamping shock

The aim of the study was to evaluate the enzyme activity of cellular membranes (GGT), cytosol (ALT, AST) and lysosome (AP, AcP) in the cytosol, whole homogenate and blood serum during declamping shock, following release of abdominal aorta cross-clamping. The aorta was clamped for 60 minutes. An increase in GGT, AP and AcP activities in the cytosol and whole homogenate of the renal cortex, renal medulla, liver, lung, heart and the skeletal muscle occurs after declamping. Rise in the enzymatic activity, especially of acid phosphatase is higher when the aorta above renal arteries was clamped. However, its activity in the blood serum remains unchanged. Alterations in the distribution and the activity of the studied enzymes may indicate that aortic clamping damages the endoplasmic reticulum and lysosomal membranes. Yet, cellular membranes preserve their structural and functional integrity.