Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.9 (enterokinase)
 675 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium ions are shown to have a marked pH-dependent effect on the kinetics of benzoyllarginine ethyl ester hydrolysis by porcine enteropeptidase (EC 3.4.21.9). Below pH 6.0, calcium ions stimulate benzoylarginine ethyl ester hydrolysis but inhibit this activity above pH 6.0. This effect is mainly on the Km for benzoylarginine ethyl ester. At pH 5.3, 2mM calcium ions reduce the Km for benzoylarginine ethyl ester from 0.31 mM to 0.26 mM while at pH 6.5 the Km increases four-fold from 0.035 mM to 0.12 mM in the presence of calcium ions. Enteropeptidase activity is not inhibited by ethylenediaminetetra-acetate indicating that calcium ions are a non-essential cofactor for benzoylarginine ethyl ester hydrolysis.
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PMID:The effect of calcium ions on the hydrolysis of benzoylarginine ethyl ester by porcine enteropeptidase. 1 Sep 92

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

Bile acids increase the release of human enteropeptidase as well as other brush-border enzymes (alkaline phosphatase, leucine aminopeptidase) from duodenal mucosa, as had been shown earlier in experimental animals. The action of bile acids is independent of their known enhancing effect on enteropeptidase activity. The pH of duodenal juice is an important, hitherto unrecognized, factor in the release mechanism of brush-border enzymes. All of the above enzymes tested were released to a markedly greater extent at pH 8.2 than 6.3, regardless of the presence or absence of bile acid. Contrary to some results obtained with animal tissue, by other investigators, our experiments with human duodenal mucosa indicate that enteropeptidase, under all conditions tested, is released at a rate considerably greater than that for alkaline phosphatase or leucine aminopeptidase. The looser association of enteropeptidase with cellular components relative to that of other brush-border enzymes, as indicated by our observations, may be related to the unique function of enteropeptidase as the trigger enzyme of protein digestion.
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PMID:Effect of bile acids and pH on the release of enteropeptidase in man. 2 91

The formation of complexes between human trypsinogens and the basic pancreatic trypsin inhibitor is demonstrated by using affinity chromatography on Sepharose coupled to basic pancreatic trypsin inhibitor. This interaction indicates the pre-existence of the active site in human trypsinogens. This active site induces the proteolytic activity of the two zymogens which activate spontaneously at pH 5.6 and pH 8.0 before and after affinity chromatography. The effect of affinity-chromatography on trypsinogen spontaneous activation is not the same on trypsinogens 1 and 2. A striking difference appears between the activation of the two trypsinogens. In all cases, trypsinogen 1 autoactivates more rapidly than trypsinogen 2, except at pH 5.6 in the presence of 10 mM Ca2+, which inhibits the autoactivation of trypsinogen 1. The effect of inherent proteolytic activity of human trypsinogens is discussed in relation to pathological conditions of enterokinase deficiency and acute pancreatitis.
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PMID:The two human trypsinogens. Evidence of complex formation with basic pancreatic trypsin inhibitor-proteolytic activity. 4 Jun 7

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

Intraductal administration of enterokinase in rats produced hyperamylasemia and acute hemorrhagic pancreatitis. The experimental pancreatitis and hyperamylasemia could be prevented by the concomitant intraductal injection of fluorouracil, pituitrin, or chlorophyll-a. The clinical implication of the study is that these agents, if given intraductally, may be useful in the prevention of iatrogenic hyperamylasemia and acute pancreatitis that may occur after endoscopic retrograde pancreatocholangiography.
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PMID:Effect of chlorophyll-a, fluorouracil, and pituitrin on experimental acute pancreatitis. 8 61

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


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