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

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

The active site of porcine enteropeptidase (EC 3.4.21.9) was investigated in order to characterize better both catalytic and binding sites. The participation of a serine and a histidine residue in the catalytic process was fully confirmed and the two residues were located on the light chain of the enzyme. The binding site was found to be composed of at least 2 subsites S1 and S2. The subsite S1 (similar to the trypsin-binding site) is responsible for the interactions with the small substrates of trypsin and the lysine side chain of trypsinogen, while subsite S2 (probably a cluster of lysines) is responsible for the interactions with the polyanionic sequence found in all trypsinogens. Binding of substrate by subsite S2 led to an increased efficiency of the catalytic site which can be correlated to the known high specificity of enteropeptidase.
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PMID:On the catalytic and binding sites of porcine enteropeptidase. 1 10

A sensitive procedure is described for the determination in duodenal aspirates of enteropeptidase activity based on the activation of trypsinogen and the estimation of trypsin formed with benzoyl-arginine-p-nitroanilide. Using the recovery approach where a known amount of purified human enteropeptidase is diluted in duodenal fluid and the recoverable activity determined, this method was shown to give a sensitive and reliable estimate of the enteropeptidase activity in duodenal fluid although it was shown that the enzyme was subject to a 10% activation by components in the duodenal fluid. The reported 5-fold stimulation of enteropeptidase activity by bile salts could not be demonstrated.
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PMID:Determination of enteropeptidase activity in human duodenal aspirates. 1 79

A continuous flow method has been developed for the automatic determination of enterokinase in rat small intesstine mucosa and/or luminal content. Trypsinogen was first hydrolysed by enterokinase under conditions which minimize autocatalytic activation. L-benzoyl-arginine paranitroanilide was then added and split to paranitroaniline by the trypsin so formed. Liberated paranitroalinine was diazotized and converted by the Bratton-Marshall reagent (N-naphthyl ethylene diamine) to an azodye, with maximum absorption at 550 nm. This method of determination was found to be six times more sensitive than the direct p-nitroaniline determination method. 36 determinations can be made hourly.
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PMID:An automated continuous flow procedure for the determination of enterokinase. 4 Jul 19

Premature activation of proteolytic zymogens (trypsinogen, chymotrypsinogen) as an early step in the pathogenesis of exocrine pancreatic insufficency (EPI) syndrome in CBA/J mice was investigated in electrophoresed pancreatic homogenates. Polyacrylamide gels containing extracts from control pancreas required prior activation of trypsinogen and chymotrypsinogen (with exogenously added enterokinase and trypsin, respectively) to produce activity staining with specific synthetic substrates. On the contrary, bands of activity staining in gels containing homogenates from mice with EPI syndrome could be readily detected without trypsin or enterokinase preincubation. Subcellular fractionation of control and diseased pancreas revealed that the premature intracellular proteolysis was confined to the zymogren granule fraction, which, even in very moderately affected pancreases (10 to 30% acinar cell autolysis), was very labile in vitro. These proteolytic events reflect the biochemical consequences of zymogen granule destabilization that were observed at the ultrastructural level.
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PMID:Exocrine pancreatic insufficiency syndrome in CBA/J mice. II. Biochemical studies. 6 19

The molecular forms of immunoreactive pancreatic cationic trypsin in sera of patients with acute pancreatic inflammation have been characterized using a radioimmunoassay technique that is capable of detecting trypsinogen as well as trypsin bound to alpha 1-antitrypsin. Trypsin bound to alpha 2-macroglobulin is not immunoreactive under normal assay conditions. However, alpha 2-macroglobulin-bound trypsin can be detected after gel filtration of serum on Bio-Gel A-0.5 m and acid treatment of column fractions. The average serum level of immunoreactive cationic trypsin from 20 patients with acute pancreatic inflammation was 1,590 ng/ml. An average normal value of 26 ng/ml has been obtained previously. Serum samples from 14 patients with pancreatic inflammation were chromatographed under conditions that resolve trypsinogen, alpha 1-antitrypsin-bound trypsin, and alpha 2-macroglobulin-bound trypsin. In each case, the major portion of the immunoreactive material eluted at a position corresponding to free trypsinogen, while a minor fraction of the immunoreactive material appeared to be trypsin bound to alpha 1-antitrypsin. The zymogen nature of the major peak was confirmed in one case by activation with human enteropeptidase. In 11 of 14 patients, acid treatment of the alpha 2-macroglobulin peak yielded immunoreactive trypsin.
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PMID:Molecular forms of immunoreactive pancreatic cationic trypsin in pancreatitis patient sera. 9 23

The activation of canine anionic and cationic trypsinogen by enterokinase, trypsin, thrombin, plasmin and extracts from canine granulocytes were studied in vitro. Enterokinase activates both trypsinogens about 1000 times faster than trypsin. The enterokinase-catalyzed activation is not inhibited by the main serum protease inhibitors, alpha-macroglobulin and alpha 1-antitrypsin. alpha-Macroglobulin cannot inhibit the activation of the trypsinogens by trypsin but this reaction is completely inhibited by alpha 1-antitrypsin. The results are discussed in relation to the pathogenesis of acute pancreatitis.
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PMID:Studies on the activation of canine trypsinogens in vitro. 9 42

A genetically conditioned mouse model of exocrine pancreatic insufficiency (epi) has been used to study the effect of the absence of lumenal proteases on small intestinal mucosal proteins. The small bowel was divided into eight equal segments. Enzyme activity was increased only in the first three segments in the case of maltase, sucrase, and lactase (all mol wt above 200,000). Alkaline phosphatase (mol wt 145,000), trehalase (mol wt 95,000), and peptidase (mol wt 175,000) activities were unaffected in proximal segments from epi mice. Proximal brush border proteins were identified and measured quantitatively by sodium dodecyl sulfate acrylamide gel electrophoresis. Those enzymes with increased activity were associated with increased amounts of protein in epi mice. Double labeled studies of protein turnover revealed a longer half-life for large brush border proteins (mol wt above 175,000) in epi mice than in normal mice. Enterokinase activity (a marker for duodenal mucosa) was nearly absent from the duodenum of epi mice. Receptors for the intrinsic factor-vitamin B12 complex (markers for ileal mucosal) were present in the ileum equally in normal and in epi mice. Enterokinase activity can be induced in epi mice by feeding its substrate trypsinogen, but not by trypsin or chymotrypsinogen. Epi mice thus retain the ability to synthesize enterokinase. Pancreatic proteases play an important role in the turnover of certain large mucosal proteins and in the induction of enterokinase.
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PMID:Effect of exchange exocrine pancreatic insufficiency on small intestine in the mouse. 20 83

The loop-breaking strength of various suture materials was tested over a period of 14 days during which time the sutures were incubated in vitro in saline or canine serum, bile, activated or nonactivated pancreatic juice. Under the conditions of the study, silk and nylon maintained their strength in each environment. Polyglycolic acid maintained its strength in saline, bile or serum, but gradually lost much of its strength when exposed to pancreatic juice. Catgut, both plain and chromic, disintegrated almost completely within 24-48 hours respectively when exposed to enterokinase activated pancreatic juice. Inhibition of trypsin by aprotinin (Trasylol) resulted in preservation of catgut strength but inhibition by soybean inhibitor did not. The latter findings suggest that proteolytic enzymes, other than trypsin, may be responsible for the disintegration.
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PMID:The disintegration of surgical sutures on exposure to pancreatic juice. 30 8

The release of enterokinase into human duodenal fluid was studied after intravenous injections of secretin and cholecystokinin-pancreozymin (CCK-PZ). In five control subjects there was a significant release of the enzyme after stimulation with either hormone. A similar release of enterokinase was observed after hormonal stimulation in three patients with total biliary obstruction and in four patients with pancreatic exocrine insufficiency. These results suggest that the hormone-mediated release of enterokinase is independent of bile salts and trypsin in man. This release of enterokinase into duodenal fluid may be physiologically important in protein digestion.
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PMID:The release of enterokinase following secretin and cholecystokinin-pancreozymin in man. 39 1

1. The serum proteinase inhibitors alpha 1-antitrypsin, alpha 2-macroglobulin, inter-alpha-trypsin inhibitor and C1-esterase inhibitor were found not to affect the catalytic activity of human enterokinase, whereas bovine trypsin activity was modified essentially as expected. Enterokinase was also not inhibited by Trasylol (trypsin inhibitor from bovine lung) or bovine pancreatic trypsin inhibitor. No other component in human or mouse serum complexing with enterokinase was identified. 2. Human enterokinase administered intravenously into mice was rapidly cleared from the circulation with a half-life of 2.5 min. This removal was not the result of the difference in species, since partially purified mouse enterokinase was cleared at the same rate as the human enzyme. Clearance was mediated by recognition of the carbohydrate portion of enterokinase and not through specific recognition of its catalytic site. Immunofluorescent staining showed that the enzyme accumulated in the liver. Attempts to block the clearance by the simultaneous infusion of competing glycoproteins suggested that enterokinase was taken up by hepatocytes. Of the glycoproteins tested only two, human lactoferrin (terminal fucosyl alpha 1 leads to 3 N-acetylglucosamine) and bovine asialo-fetuin (terminal galactosyl beta 1 leads to 4 N-acetylglucosamine) were weakly competitive. Two inhibitors of endocytosis, Intralipid and Triton WR1339, failed to delay the removal of enterokinase. It is proposed that enterokinase is cleared from the circulation by an as yet uncharacterized hepatocyte receptor.
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PMID:Identification of a defence mechanism in vivo against the leakage of enterokinase into the blood. 39 51


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