Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.56 (insulin-degrading enzyme)
 737 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The degradation of insulin by insulin protease and glutathion-insulin transhydrogenase (glutathioneproteindisulphide oxidoreductase--EC 1.8.4.2, GIT) was measured in rat liver either after replacing food and water by 15% glucose solution, or after daily insulin administration 8 U daily for 3 days or after fasting. The breakdown of radioiodinated insulin was followed by measuring the increase of TCA soluble radioactivity during incubation of cell fractions with 125I insulin at 37 degrees C. The highest GIT activity was observed in liver microsomes of rats after glucose feeding and after insulin administration, whereas enzyme activity of fasted animals did not essentially differ from corresponding values of normally fed controls. The insulin protease in cytosol of liver cells remained unchanged after these procedures. The important role of GIT in insulin degradation seems to be conclusively demonstrated.
Endocrinol Exp 1977 Sep
PMID:Effect of insulin and glucose on the activity of insulin-degrading enzymes in rat liver. 30 91

Calcium chloride increased the liver insulinase activity (LIA) in normal rabbits. No significant changes were noted in the plasma insulinlike activity (PILA), serum zinc level (SZ), and pancreatic zinc content (PZ). Insulin elevated PILA, SZ and PZ but did not affect LIA. Calcium chloride enhanced the effect of insulin on PILA, SZ and PZ. However, insulin did not affect the action of calcium chloride on LIA. Tolbutamide raised PILA, inhibited both LIA and SZ but did not affect PZ. Calcium chloride produced no change in the action of tolbutamide on PILA. On the other hand, tolbutamide prevented the rise of PILA obtained by calcium chloride. PZ was unaltered with calcium chloride and tolbutamide combination. Phenformin increased PILA, LIA, SZ and PZ. When it was given with calcium chloride no further changes in PILA and PZ were observed. The elevation of SZ was abolished but the rise of LIA was synergized. In alloxanized rabbits, LIA was decreased by calcium chloride. No changes were found in PILA, SZ and PZ. Insulin elevated PILA, LIA and SZ although it reduced PZ. Calcium chloride stimulated insulin effect on PILA, did not affect its action on SZ or PZ, and antagonized its effect on LIA. Tolbutamide increased LIA and SZ but did not affect PILA or PZ. Calcium chloride could not change the effect of tolbutamide on SZ or PILA although it could abolish the action of this drug on LIA and PZ. Phenformin significantly lowered PILA, LIA and PZ but raised SZ. Calcium chloride combination with phenformin produced a further decrease in LIA but no other changes in PIAL, SZ or PZ were recorded.
Pharmazie 1975 Sep
PMID:Effect of calcium chloride on some metabolic actions of certain antidiabetic drugs in normal and alloxanised rabbits. 118 41

An insulin-binding metal- and thiol-dependent proteinase has been purified 1491-fold from high speed cytosolic fractions of the fungus Neurospora crassa. This enzyme resembles insulin-degrading enzymes (insulinases) present in mammalian cells and in Drosophila melanogaster in the following ways: (i) it degrades radiolabeled insulin with a specificity similar to that of rat muscle insulinase, as demonstrated by HPLC analysis of the degradation products; (ii) it is inhibited by bacitracin, EDTA, 1,10-phenanthroline, and the sulfhydryl-reactive compounds N-ethylmaleimide and p-chloromercuribenzoate, but not by inhibitors of serine proteases or by lysosomal protease inhibitors. Cross-linking with 125I-insulin labels a band of ca. 120 kDa, and several smaller bands which may represent degradation products. The N. crassa insulinase is stimulated by Mn2+ and strongly inhibited by Zn2+; Mn2+ can also reactivate the enzyme after inhibition by EDTA, but Zn2+ is ineffective. The N. crassa protein differs in this regard from mammalian and insect insulinases which are generally activated by both Mn2+ and Zn2+. This finding extends the apparent evolutionary conservation of these metal- and thiol-dependent proteases into the microbial realm.
Arch Biochem Biophys 1992 Sep
PMID:Characterization and partial purification of an insulinase from Neurospora crassa. 138 21

Although insulin-degrading enzyme (IDE) has been implicated in the intracellular degradation of insulin, the cellular localization of this enzyme is still controversial. In the present study, we have examined the cellular localization of IDE in the rat liver by three different techniques using monoclonal antibodies. First, direct immunohistochemical staining of rat liver with one of the monoclonal antibodies revealed that IDE immunoreactivity mainly exists in parenchymal cells, especially in the vicinity of the portal tract and also in the epithelium of the bile duct under light microscopy. In the electron microscopic study, IDE immunoreactivity was found in the cytoplasm near the rough endoplasmic reticulum but not in the plasma membrane, nucleus, or mitochondria. Second, immunoblotting analysis of the subcellular fraction in rat liver showed that the monoclonal antibody specifically reacted with a single polypeptide in the cytosolic fraction, of apparent Mr 110,000, which was consistent with the Mr of IDE. However, a polypeptide band corresponding to IDE could not be observed in the plasma membrane, mitochondrial, or lysosomal fraction. Third, IDE was only detectable in the cytosolic fraction by sandwich radioimmunoassay using two monoclonal antibodies. These results all suggest that IDE is a cytosolic enzyme.
Biochem Biophys Res Commun 1988 Sep 15
PMID:Cellular localization of insulin-degrading enzyme in rat liver using monoclonal antibodies specific for this enzyme. 304 64

The degradation of insulin by the enzyme insulin protease and by isolated hepatocytes results in proteolytic cleavages in both the A and B chains of intact insulin. Previous studies have shown that one of the A chain cleavages is between A13 leucine and A14 tyrosine and that a second cleavage occurs carboxyl to the A14 residue. In the present study we have used insulin specifically iodinated on the A19 tyrosine and examined the A chain cleavages by the enzyme and by hepatocytes. Insulin degradation products were purified by HPLC and sequenced by automated Edman degradation. Only two A chain cleavage sites were identified, one the previously reported A13-A14 and the other between A14 tyrosine and A15 glutamine. These data thus identify the second A chain cleavage site and further support the role of insulin protease in hepatic metabolism of insulin.
Biochem Biophys Res Commun 1987 Sep 15
PMID:Identification of A chain cleavage sites in intact insulin produced by insulin protease and isolated hepatocytes. 330 83

A method has been described for the direct measurement of proinsulin in human plasma. The method makes use of an insulin-degrading enzyme designated "insulin-specific protease (ISP)", which is obtained from rat skeletal muscle. Under the conditions used, this enzyme rapidly degrades insulin and insulin-like polypeptides to nonimmunoassayable components, whereas proinsulin and proinsulin cleaved at position B(54,55) are not appreciably affected. The incubation of plasma with ISP results in the disappearance of insulin, but not proinsulin, as demonstrated by column chromatography. Immunoassay of the plasma, therefore, before and after incubation, determines the values for the total immunoreactive substance (TIR) and for immunoreactive proinsulin (IRP), respectively. The values obtained for proinsulin levels are reproducible and compare closely with the more complicated column fractionation methods. Proinsulin responses were studied in four normal subjects and one patient with an insulinoma after a glucose load. Fasting proinsulin levels varied widely in the normal subjects, and the levels rose more slowly than TIR levels after glucose. IRP levels in the patient with an insulinoma were very high and fell to normal after removal of the tumor. The ISP method, therefore, appears to be suitable for the direct, accurate, and rapid determination of proinsulin and proinsulin-like materials in human plasma.
J Clin Invest 1971 Sep
PMID:Direct measurement of proinsulin in human plasma by the use of an insulin-degrading enzyme. 432 76

The kidney plays a pivotal role in the clearance and degradation of circulating insulin and is also an important site of insulin action. The kidney clears insulin via two distinct routes. The first route entails glomerular filtration and subsequent luminal reabsorption of insulin by proximal tubular cells by means of endocytosis. The second involves diffusion of insulin from peritubular capillaries and subsequent binding of insulin to the contraluminal membranes of tubular cells, especially those lining the distal half of the nephron. Insulin delivered to the latter sites stimulates several important processes, including reabsorption of sodium, phosphate, and glucose. In contrast, insulin delivered to proximal tubular cells is degraded to oligopeptides and amino-acids by one of two poorly delineated enzymatic pathways. One pathway probably involves the sequential action of insulin protease and either GIT or non-specific proteases; the other probably involves the sequential action of GIT and lysosomal proteases. The products of insulin degradation are reabsorbed into the peritubular capillaries, apparently via simple diffusion. Impairment of the renal clearance of insulin prolongs the half-life of circulating insulin by a number of mechanisms and often results in a decrease in the insulin requirement of diabetic patients. Much needs to be learned about these metabolic events at the subcellular level and how they are affected by disease states. Owing to the heterogeneity of cell types within the kidney and to their anatomical and functional polarity, investigation of these areas will be challenging indeed.
Diabetologia 1984 Sep
PMID:The renal metabolism of insulin. 638 40

The specificity of insulin proteinase (EC 3.4.99.45) has been difficult to categorize using only its natural substrates. By exploiting the fact that two substrates competing for the same enzyme inhibit one another, we have found some new substrates of the insulin proteinase from porcine muscle. Two of these substrates, a tryptic fragment of BSA and a fragment of cytochrome c, have been shown to be cleaved at a single site. The albumin fragment, as well as another fragment of cytochrome c., have susceptibilities (Vmax/Km) comparable with that of insulin. In a second aspect of the study, the porcine-muscle enzyme was shown to be related to other members of its superfamily in that it was immunoprecipitated by a monoclonal antibody raised against the insulin-degrading enzyme from human red blood cells and has the same cleavage sites on insulin as has the rat skeletal-muscle insulin proteinase. We note, however, a possible discrepancy between our results and those of another group regarding the subunit size (110 kDa) of the immunoprecipitated material.
Biochem J 1994 Sep 15
PMID:Preparation and characterization of novel substrates of insulin proteinase (EC 3.4.99.45). 794 19

Insulin degrading enzyme (IDE) is an evolutionarily conserved, nonlysosomal metalloprotease that has been implicated in the cellular degradation and processing of insulin. However, the site and the mode of the action of this enzyme are unclear. We have addressed these questions by establishing several Ltk- cell lines that can overexpress human insulin-degrading enzyme (hIDE) upon glucocorticoid induction. The level of overexpression of hIDE protein and transcripts in these lines correlates well with an increase in insulin degradation in both cell lysates and intact cells. Comparison of the deduced amino acid sequences of mammalian and Drosophila IDEs reveals a conserved carboxyl-terminal peroxisomal targeting sequence (A/S-K-L), suggesting that IDE may be localized in peroxisomes. To test this possibility, we determined the cellular location of the stably transfected hIDE by both immunofluorescence and immunocryoelectron microscopy. The overexpressed hIDE predominantly colocalized with catalase in peroxisomes, although IDE was also found in the cytosol at a much lower concentration. These results demonstrate that stably transfected IDE catalyzes a rate-limiting step in cellular insulin degradation and is localized predominantly in peroxisomes.
J Biol Chem 1994 Sep 09
PMID:Inducible expression and cellular localization of insulin-degrading enzyme in a stably transfected cell line. 807 10

Insulin cellular degradation was studied in cultured 18-day-old fetal rat hepatocytes in the presence and absence of insulin degradation inhibitors that decrease the glycogenic response to insulin. After cell incubation with 3 nM [125I]A14 or -B26 insulin, hormone degradation products associated with cells or present in the medium were analyzed by high-performance liquid chromatography. Within cells, four components containing intact [125I]A14 insulin A-chain and part of the B-chain (A1-A4, according to increasing retention times) were found together with two [125I]B26 insulin B-chain COOH-terminal fragments (B1 and B2). Medium degradation intermediates comprised B1 and B2 but not A1-A4. Cellular insulin fragments A3 and B2 exhibited a maximal transient accumulation after 2 min, whereas the others increased progressively to plateau after 10 min. Chloroquine inhibited the formation of A1, A2, and B1 by 70-80%, whereas that of A3, A4, and B2 was not significantly affected. N-ethylmaleimide and bacitracin, two inhibitors of insulin-degrading enzyme (IDE), decreased the formation of chloroquine-dependent cellular peptides. Thus cell-associated insulin degradation implied primarily two cleavages in B-chain near the COOH-terminus, the one sensitive to chloroquine and IDE inhibitors occurring after endosomal segregation of insulin and its receptor.
Am J Physiol 1996 Sep
PMID:Sequential insulin degradation in cultured fetal hepatocytes in relation to chloroquine-dependent events. 884 33


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