Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We point out that human low-Mr kininogen contains three cystatin-like sequences, rather than two, as had previously been thought. The protein was purified by affinity chromatography on carboxymethyl-papain-Sepharose, and subjected to limited proteolysis by trypsin and chymotrypsin. Fragments were isolated, and three corresponding to the individual cystatin-like domains were identified. By comparison with the known amino acid sequence of the protein they were numbered 1 to 3 from the N-terminus. Domain 1 was not found to have any inhibitory activity for cysteine proteinases, which is consistent with the absence of residues that are highly conserved in inhibitors of the cystatin superfamily, and have previously been suggested to be essential for activity. Domain 2 was a good inhibitor of chicken calpain, and also papain and cathepsin L. Domain 3 showed negligible inhibition of calpain, but inhibited papain and cathepsin L strongly. The probable arrangement of disulphide bonds in the heavy chain of low-Mr kininogen is deduced from the homology with the cystatins and other evidence contained in the present paper.
...
PMID:Human low-Mr kininogen contains three copies of a cystatin sequence that are divergent in structure and in inhibitory activity for cysteine proteinases. 352 86

High molecular weight (HMW) kininogen was purified from fresh human plasma by two successive column chromatographies on DEAE-Sephadex A-50 and Zn-chelate Sepharose 4B. The purified HMW kininogen appeared to be a single band on sodium dodecyl sulfate (SDS)-polyacrylamide disc gel electrophoresis in both the presence and absence of beta-mercaptoethanol. However, it gave two bands on nonreduced SDS-polyacrylamide slab gel electrophoresis, a major band of dimeric form (Mr 200 000, ca. 95%) and a minor band of monomeric form (Mr 105 000, ca. 5%). Under reduced conditions, the dimeric form was converted stoichiometrically to a monomeric form (Mr 110 000), and the monomeric form observed under nonreduced conditions (Mr 105 000) was converted to a heavy chain (Mr 60 000) and a light chain (Mr 50 000). The formation of a dimer of HMW kininogen was also confirmed by an immunoblotting experiment. This unique property of intact HMW kininogen to form a dimer was further utilized in studies on the kininogens and their derivatives as thiol proteinase inhibitors. The purified HMW kininogen strongly inhibited the caseinolytic activities of calpain I, calpain II, and papain but not those of trypsin, chymotrypsin, and thermolysin, indicating that it was a group-specific inhibitor for thiol proteinases. When HMW kininogen was reduced with 0.14 or 1.4 M beta-mercaptoethanol, its inhibitory activity was partially or mostly inactivated, but on subsequent air oxidation its activity was almost completely recovered. In addition, kinin-free and fragment 1,2 free HMW kininogen showed higher inhibitory activity than the intact HMW kininogen.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Human high molecular weight kininogen as a thiol proteinase inhibitor: presence of the entire inhibition capacity in the native form of heavy chain. 363 11

A 34,000-dalton inhibitor of calpain (Ca2+-dependent cysteine proteinase) was found in the cytosol of anemic rat liver. When phenylhydrazine hydrochloride was continuously administered to rats, a 280,000-dalton calpain inhibitor that existed originally in the liver gradually disappeared within two weeks and, concomitantly, a 34,000-dalton inhibitor appeared. The purified 34,000-dalton inhibitor resembles 280,000-dalton inhibitor in that both are heat-stable proteins and do not inhibit papain and trypsin. Unlike the protomers of a 280,000-dalton inhibitor, 34,000-dalton inhibitor does not show any sign of self-association.
...
PMID:The appearance of a 34,000-dalton inhibitor of calpain (Ca2+-dependent cysteine proteinase) in rat liver after the administration of phenylhydrazine. 631 91

The major components of neurofibrillary tangles (NFT) in Alzheimer's disease are bundles of paired helical filaments (PHF) which are primarily composed of highly phosphorylated tau proteins (PHF-tau). To further understand the mechanism of PHF accumulation in NFT, we examined the calpain-induced proteolysis of highly purified and primarily non-aggregated PHF and normal tau proteins with various contents of phosphate isolated from either fetal (F-tau) or adult human brain (N-tau). The extent of proteolysis was determined by decreases in tau immunoreactivity using Western-blot analysis and a panel of site-specific tau antibodies (Alz 50, Tau-2, Tau 14, Tau-1, AT8, E-11, AH-1 and PHF-1). We found that full-size polypeptides of N-tau and F-tau were similarly and rapidly proteolyzed in vitro by calpain (calpain II, 3.3 units/mg protein) during a 10-min incubation at 30 degrees C, and that their half lives (t1/2) were 1.5 min and 1.8 min, respectively. Analysis of immunoblots suggests that full-length polypeptides of tau are first degraded into large fragments similar in size to that generated endogenously, then into smaller fragments. Since both endogenous and in-vitro-generated tau fragments retained N-terminal epitopes, the results suggest that most of the calpain-sensitive sites may be located in the C-terminal half of the tau molecule. In contrast, PHF were extremely resistant to degradation and only a fivefold higher concentration of calpain (16.7 units/mg protein) induced partial proteolysis of PHF. A major calpain-generated fragment was a 45-kDa polypeptide derived from the C-terminal region of PHF-tau, which forms a core of filaments. The results suggest that the inaccessibility of potential calpain-digestion sites in the filament core could contribute to the resistance of PHF to calpain and subsequently lead to the accumulation of PHF in Alzheimer's disease. The results also suggest that hyperphosphorylation of tau may be marginally involved in the resistance of PHF to degradation by calpain. Ultrastructural examination revealed that, in contrast to previous studies with trypsin, calpain did not alter the morphologic appearance of filaments; after incubation with calpain, the majority of PHF remained short and disperse and the number of PHF aggregated into NFT-like clusters was not significantly increased. The results suggest that the role of calpain in promoting the aggregation and clustering of filaments is limited.
...
PMID:Calpain-induced proteolysis of normal human tau and tau associated with paired helical filaments. 758 78

Reduced turn-over of tau by calpains is a possible mechanism to facilitate the incorporation into paired helical filaments (PHFs) in Alzheimer's disease. The present study shows that the differently phosphorylated fetal tau isoforms are all rapidly proteolysed to an equal extent by human brain m-calpain. This result argues against the hypothesis that this type of fetal phosphorylation is involved in reducing tau turn-over by calpain in Alzheimer's disease. Adult and fetal tau fragments in vitro generated by m-calpain, but not trypsin, cathepsin D or chymotrypsin resemble the post-mortem in situ degradation patterns, suggesting a possible role for calpains in tau metabolism in vivo. Tau incorporated into PHFs was considerably more resistant to proteolysis by calpain which can help to explain the persistence of these structures in Alzheimer's disease.
...
PMID:Differential sensitivity to proteolysis by brain calpain of adult human tau, fetal human tau and PHF-tau. 761 58

Cleavage of Shiga toxin A-fragment at a highly trypsin-sensitive site increases its enzymatic activity. To investigate the role of this cleavage site in intoxication of cells, we studied the routing, cleavage, and toxicity of mutant toxin where the trypsin-sensitive site had been eliminated. Ultrastructural analysis of toxin tagged with horseradish peroxidase demonstrated that wild-type and mutant toxins were transported from endosomes to the trans-Golgi network and further through the Golgi cisterns to the endoplasmic reticulum. Wild-type toxin was much more efficient than the mutants in provoking rapid intoxication, but after prolonged incubation time also mutants were highly toxic. The cells were able to cleave both wild-type Shiga toxin and the mutants, but the cellular location for cleavage appears to differ. Wild-type toxin was cleaved in the presence of brefeldin A, which disrupts the Golgi cisterns. This indicates that the cleavage occurs in the endosomes or in the trans-Golgi network. In contrast, the mutant Shiga-His (R248H/R251H) was not cleaved in the presence of brefeldin A, indicating that the cleavage can occur only after the toxin has left the trans-Golgi network. In vitro experiments showed that the cytosolic enzyme calpain is able to cleave Shiga-His, and results from in vivo experiments are consistent with the possibility that cleavage is carried out by calpain after the mutant A-fragment has reached the cytosol.
...
PMID:Role of processing and intracellular transport for optimal toxicity of Shiga toxin and toxin mutants. 773 76

Amyloid beta protein (beta/A4) is deposited in senile plaques of patients with Alzheimer's disease. This protein is derived from a larger membrane-associated protein, termed amyloid precursor protein (APP). The constitutive processing of APP occurs at the central portion of beta/A4, resulting in the release of large N-terminal peptides. We have purified these peptides from the culture medium of cDNA-transfected COS-1 cells. Some of the isoforms contain the Kunitz-type protease inhibitor (KPI) domain and strongly inhibit trypsin, chymotrypsin and plasmin, but do not inhibit kallikrein, prolyl endopeptidase or granzyme A. The peptides also do not inhibit cysteine proteases such as cathepsin B or calpain. Soluble APPs lacking the KPI domain fail to inhibit any of these proteases. The results indicate that the KPI domain in soluble APPs has protease inhibitory activity against certain serine proteases.
...
PMID:Inhibitory spectra of purified protease nexin-II and related proteins towards cellular proteinases. 790 50

A calcium dependent proteolytic enzyme was detected in the lysed promastigotes of Leishmania donovani, the causative agent of kala-azar. The protease was able to hydrolyse an added substrate, azocasein and showed high affinity for calcium. Rate of azocasein digestion was primarily slow but boosted up after eight hours. It was not inactivated when heated at 55 degrees C for 15 min at pH 7.4. Sulfhydryl reagents significantly reduced the enzymic activity but trypsin-like protease inhibitors hardly had any effect. The enzyme was not sensitive to calmodulin from a heterologous source but registered low activity when treated with chlorpromazine. The caseinolytic activity was stimulated when leishmanial cells were preincubated with ionophore A23187 in presence of 1 mM Ca2+. The enzyme is named caldonopain due to its similarity with a general class of calcium dependent protease calpain present in different tissues and cells. Caldonopain was found to be localized in cytosol along with its specific endogenous inhibitor caldonostatin. The ratio of caldonopain-caldonostatin unit was higher in the infected macrophage compared to the parasitic protozoa and Balb/c macrophage alone. It may be postulated that the amount of both calcium and its protein inhibitor may have a direct impact on the caldonopain-induced biological process to regulate cellular action of this pathogen.
...
PMID:Calcium dependent thiol protease caldonopain and its specific endogenous inhibitor in Leishmania donovani. 810 94

Platelet glycocalicin (GC) is the extramembranous portion of GPIb alpha that can be rapidly cleaved by enzymes such as calpain, plasmin, trypsin, elastase, etc. Quantitative cleavage will ultimately result in an acquired Bernard-Soulier-like bleeding disorder, and circulating GC may act as a potential inhibitor of platelet adhesion. We have developed and standardized a new enzyme-linked immunosorbent assay (ELISA), which uses two monoclonal antibodies (mAbs), both of which bind to the amino-terminal 45-kD fragment of GC and inhibit platelet-von Willebrand interactions and the streptavidin-biotin system. First, the methodology was evaluated and standardized with special emphasis on the anticoagulant and the inhibitors (EDTA, prostaglandin E1 [PGE1], aprotinin, N-ethyl-maleimide), the mode of high-speed centrifugation (to avoid platelet microparticles), and the standards used (purified GPIb and GC). This assay was then used to analyze the GC levels of healthy subjects (2.04 +/- 0.46 micrograms/mL) and of patients with selected diseases. The results of patients with aplastic anemia and thrombocytosis confirmed that GC levels are clearly dependent on the platelet count, which was the basis for the introduction of the GC index, the standardization of GC for a platelet count of 250 x 10(9)/L. The GC index discriminates reliably patients with active immune thrombocytopenic purpura from those in remission. GC levels are elevated in patients on hemodialysis (3.62 +/- 0.75 micrograms/mL, P < .001). The high GC index (6.93 +/- 4.21, P < .001) in cirrhosis patients suggests an increased platelet turnover and/or abnormal proteolysis. In contrast to other groups, we have not found that recombinant tissue plasminogen activator (rtPA) treatment of patients with myocardial infarction increases GC levels. However, concentrations are elevated in leukemia and the highest levels found are approximately 40 micrograms/mL. These studies suggest that GC is a useful platelet marker in certain diseases, which directly reflects platelet damage and possibly platelet dysfunction.
...
PMID:Glycocalicin: a new assay--the normal plasma levels and its potential usefulness in selected diseases. 829 32

Isolated connexin-32s from rat and mouse liver are proteolyzed in vitro by the intracellular Ca(2+)-dependent neutral proteases, mu-calpain and m-calpain, producing a major fragment of 26 kDa. Connexin-26 is not proteolyzed by calpain. Calpain cleaves connexin-32 at its C-terminal end as shown by 125I-calmodulin binding experiments. Connexin-32, but not connexin-26, is phosphorylated by both protein kinase A and protein kinase C in serine residues and the sites of phosphorylation by both kinases remain in the major 26-kDa fragment resulting from calpain proteolysis. Phosphorylation of connexin-32 by protein kinase C, but not by protein kinase A, prevents the proteolytic attack of mu-calpain and m-calpain. Phosphorylation of connexin-32 by protein kinase A and protein kinase C does not prevent its proteolysis by papain, alpha-chymotrypsin, proteinase K, and trypsin.
...
PMID:Phosphorylation of connexin-32 by protein kinase C prevents its proteolysis by mu-calpain and m-calpain. 839 Sep 88


<< Previous 1 2 3 4 5 6 7 8 Next >>

---