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:3.4.21.1 (chymotrypsin)
10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nascent polysome-associated type I procollagen pro-alpha-chains isolated from chick embryo tendon fibroblasts were examined for their proteinase resistance. The distribution of chain sizes and their proteinase resistance were also determined following chain elongation in an in vitro readout system in the absence of chain initiation factors. Chains were labeled with [14C]proline in the cells and with [3H]proline in the readout system. Differences in the ratios of 14C to 3H in the double-labeled nascent chains before and after chymotryptic digestion, determined by slicing and counting polyacrylamide gels after electrophoresis, permitted analysis of the relative stabilities of in vivo and in vitro elongated portions of the chains. In confirmation of earlier work, the polysome-bound nascent procollagen contained chymotrypsin, chymotrypsin plus trypsin, and pepsin-resistant alpha-chain size components. The readout system data showed that the full length chains produced in the cell were more resistant to digestion than the fully elongated readout-completed chains. The protease resistance of the chains was taken to indicate the registration of the chains prior to the induction of helix formation during the isolation procedure. These data support the model in which chain selection and folding are facilitated by the organization of the attachment of the ribosomes to the endoplasmic reticulum surface.
...
PMID:The coordinate synthesis and cotranslational assembly of type I procollagen. 264 82

The simian rotavirus SA11 genome segment 10 codes for a nonstructural glycoprotein, NS28, that has been hypothesized to be involved in budding of viral particles into the endoplasmic reticulum (ER) membrane. Previous studies had suggested that NS28 is an integral membrane protein of the ER, possibly a transmembrane protein. We have examined the topography of NS28 inserted in microsomal membranes following cell-free translation of genome segment 10 transcripts. These transcripts were obtained either by hybrid selection of mRNA synthesized by the endogenous viral RNA polymerase or by in vitro transcription of genome segment 10 cDNA using SP6 polymerase. Full-length and truncated gene 10 transcripts were translated in a cell-free system supplemented with dog pancreatic microsomes. The existence of a cytoplasmic domain of the translation product was demonstrated by protease protection experiments. An 18,000 (18K) mol wt glycosylated polypeptide was protected from digestion with proteinase K and trypsin, whereas chymotrypsin digestion yielded a 23K mol wt glycosylated polypeptide. Correlation of these biochemical data with the known sequence of NS28 suggests that a 10K mol wt hydrophilic, carboxy-terminal fragment (from amino acid number 86 to amino acid number 175) of this glycoprotein is exposed on the cytoplasmic side of the ER membrane. A model of how NS28 folds in the ER membrane is proposed.
...
PMID:Topography of the simian rotavirus nonstructural glycoprotein (NS28) in the endoplasmic reticulum membrane. 283 61

Approximately the same levels of six of the seven enzymes catalyzing reactions of the pentose phosphate pathway are in the cisternae of washed microsomes from rat heart, spleen, lung, and brain. Renal and hepatic microsomes also have detectable levels of these enzymes except ribulose-5-phosphate epimerase and ribose-5-phosphate isomerase. Their location in the cisternae is indicated by their latencies, i.e. requirement for disruption of the membrane for activity. In addition, transketolase, transaldolase, and glucose-6-phosphatase, a known cisternal enzyme, are inactivated by chymotrypsin and subtilisin only in disrupted hepatic microsomes under conditions in which NADPH-cytochrome c reductase, an enzyme on the external surface, is inactivated equally in intact and disrupted microsomes. The failure to detect the epimerase and isomerase in hepatic microsomes is due to inhibition of their assays by ketopentose-5-phosphatase. Xylulose 5-phosphate is hydrolyzed faster than ribulose 5-phosphate. A mild heat treatment destroys hepatic xylulose-5-phosphatase and glucose-6-phosphatase without affecting acid phosphatase. These results plus the established wide distribution of glucose dehydrogenase, the microsomal glucose-6-phosphate dehydrogenase, and its localization to the lumen of the endoplasmic reticulum suggest that most mammalian cells have two sets of enzymes of the pentose phosphate pathway: one is cytoplasmic and the other is in the endoplasmic reticulum. The activity of the microsomal pentose phosphate pathway is estimated to be about 1.5% that of the cytoplasmic pathway.
...
PMID:The pentose phosphate pathway in the endoplasmic reticulum. 284

The biosynthesis and maturation of human sucrase-isomaltase (SI, EC 3.2.1.48-10), was studied in cultured small intestinal biopsy specimens and mucosa explants. Pulse-chase experiments with [35S]methionine revealed one high mannose intermediate of Mr = 210,000 (pro-SIh) which was processed at a slow rate to an endo H-resistant, mature form of Mr = 245,000 (pro-SIc). The fully core-glycosylated form (Mr = 212,000) was detected only when 1-deoxynojirimycin was added to the culture medium, thus indicating that the core sugars undergo rapid processing by rough endoplasmic reticulum membrane-bound glycosidases. The data presented showed that trypsin specifically and instantaneously (within 1 min) cleaves pro-SIc to two subunits Ic (Mr = 145,000) and Sc (Mr = 130,000). Elastase and chymotrypsin are not effective. Enzymic and chemical deglycosylations of SI with endo-beta-N-acetylglucosaminidase F/glycopeptidase F and trifluoromethanesulfonic acid (TFMS) as well as probing for the binding capacity of SI to Helix pomatia lectin demonstrated that pro-SIc, Ic, and Sc are N- and O-glycosylated. Furthermore, the results were indicative of a posttranslational O-glycosylation of pro-SI, since (i) the earliest detectable precursor form, pro-SIh, did not bind to H. pomatia lectin and (ii) its deglycosylation products with both endo-beta-N-acetylglucosamidase H and TFMS were identical. Both the Sc and Ic subunits contain eight N-linked glycan units, at least one of which is of the high mannose type and found on Sc. Finally, Sc, but not Ic, was shown to display at least four populations varying in their content of O-linked glycans. The heterogeneous O-glycosylation pattern of Sc could be correlated with the distal position of this subunit (and its O-glycosylation sites) within the pro-SI molecule, thus affecting the extent of O-linked oligosaccharide processing and their subsequent presentation on the mature molecule.
...
PMID:Biosynthesis of the human sucrase-isomaltase complex. Differential O-glycosylation of the sucrase subunit correlates with its position within the enzyme complex. 336 77

Solid and papillary epithelial neoplasms of the pancreas from six female patients were studied using immunohistochemistry and electron microscopy to define better their histogenesis. The tumors ranged in diameter from 5 to 15 cm (average: 9 cm), and, on cross section, most had areas of hemorrhage and necrosis, sometimes extensive. Microscopically, there was a solid and pseudopapillary pattern, with tumor cells typically having ovoid nuclei with delicate folding and indistinct nucleoli. Of note were the following: a relatively low mitotic rate (range: 0-6/20 hpf), the presence of hyaline globules (four of six cases), and collections of foam cells (three of six cases). Staining for cytoplasmic argyrophil granules was negative in each case. Ultrastructurally, the solid and papillary epithelial neoplasms of the pancreas showed evidence of acinar or ductular differentiation. Two contained zymogen granules, one had intermediate filaments (probably keratin), and three had abundant rough endoplasmic reticulum and mitochondria. Immunostaining was positive for chymotrypsin (six of six cases), trypsin (four of six), and amylase (three of six). None was positive for alpha-1-antitrypsin, neuron-specific enolase, pancreatic polypeptide, gastrin, glucagon, somatostatin, or insulin. The findings support an origin from exocrine pancreas, and follow-up indicates a low rate of malignancy, with local recurrence in two of the six patients.
...
PMID:Solid and papillary epithelial neoplasm of the pancreas. An ultrastructural and immunocytochemical study of six cases. 381 76

Chinese hamster lung cells resistant to Adriamycin were labeled with inorganic [32P]orthophosphate and thereafter incubated with low levels of N-ethylmaleimide. Plasma membranes and endoplasmic reticulum were isolated and the phosphorylated proteins were analyzed after polyacrylamide gel electrophoresis. The results demonstrate that both plasma membranes and endoplasmic reticulum from resistant cells contain two highly phosphorylated proteins [Mr 180,000 (p180) and Mr 220,000 (p220)] which are present in very low levels in these membrane fractions prepared from drug sensitive cells. p220 is present in much higher levels in the endoplasmic reticulum as compared to the plasma membranes whereas p180 is equally distributed in these two membrane fractions. When resistant cells revert to drug sensitivity there is a parallel loss in the phosphorylation levels of p180 and p220. Labeling of membrane proteins with 125I in the presence of chloramine-T also reveals that p180 and p220 are present in significantly greater levels in resistant membranes as compared to similar fractions prepared from drug sensitive cells. Partial digests of phosphorylated p180 and p220 produced with chymotrypsin or V8 protease reveal that each protein has a distinct phosphopeptide pattern. Both p180 and p220 are phosphorylated exclusively at serine residues. The results of this study therefore suggest that resistance to Adriamycin in Chinese hamster lung cells requires the involvement of two distinct proteins which are both bound to cell membranes.
...
PMID:Evidence for the involvement of two distinct membrane proteins in adriamycin resistance in Chinese hamster lung cells. 406 66

A procedure for dissociation of the guinea pig pancreas into individual cells is described which employs enzymatic digestion with pure collagenase, chymotrypsin, and hyaluronidase, utilizes an interposed chelation of divalent cations by EDTA, and is terminated by gentle shearing. Yields of cells are 50-60%, based on DNA recovered. The population comprises approximately 95% exocrine cells, the remainder consisting of endocrine, duct, and vascular endothelial cells. The exocrine cells, though spherical, retain the structural attributes of their in situ counterparts, including differentiation of the plasmalemma into zones corresponding to the former apical and basal plasmalemma, polarized distribution of organelles indicated by fields of zymogen granules in the cytoplasm underlying the former apex, central location of the Golgi complex, and placement of the rough endoplasmic reticulum and nucleus in the former basal pole of the cell. Electron microscope study of the effects of individual treatments used during dissociation indicates that digestion of basement membrane and collagen is solely due to collagenase activity and that separation of desmosomes (and possibly of zonulae adherentes) results only from exposure to low [Ca(++)] and EDTA and is not effected by the enzymes used. Gap junctions are resistant to enzymes and EDTA; tight junctions resist enzyme treatment but undergo rearrangement upon exposure to EDTA. Both junctions require mechanical shear for complete cell separation. Neither chymotrypsin nor hyaluronidase produces visible alterations in stromal or junctional elements. Dissociation requires the concerted action of enzymes, chelation of divalent cations, and mechanical shear, since the individual treatments are alone ineffective.
...
PMID:Studies on dispersed pancreatic exocrine cells. I. Dissociation technique and morphologic characteristics of separated cells. 437 77

The topography of glycerolipid biosynthetic enzymes within the transverse plane of rat liver microsomal vesicles was investigated: (1) by use of the impermeant inhibitor, mercury-dextran; (2) by use of proteases; and (3) by determining whether the enzyme activities are latent. The seven enzyme activities investigated (dihydroxyacetone-phosphate acyltransferase, acyldihydroxyacetone-phosphate oxidoreductase, phosphatidic acid : CTPcytidyltransferase, CDPdiacylglycerol : inositol phosphatidyltransferase, 2-monoacylglycerol acyltransferase, diacylglycerol kinase, and the serine base exchange enzyme) function in phosphatidylinositol and phosphatidylserine synthesis and at intermediate levels in glycerolipid synthesis including steps of ether lipid synthesis. Mercury-dextran inhibited four of these enzymes greater than 60% in intact microsomal vesicles. One or more of the proteases employed (chymotrypsin, trypsin and pronase) inactivated each of the seven enzyme activities in intact microsomal vesicles. These two approaches indicate that each of these enzymes has important domains located on the cytoplasmic surface of microsomal vesicles. These enzyme activities could be assayed in intact microsomal vesicles. None appeared to be highly latent, indicating that substrates have free access to active sites. One substrate for each of these enzymes had been shown previously to be unable to cross the microsomal membrane. These data indicate that the active sites of these enzymes are located on the cytoplasmic surface of microsomal vesicles. It is concluded that the synthesis of phosphatidylserine and phosphatidylinositol, intermediates of ether lipid formation and other intermediates of glycerolipid synthesis occur asymmetrically on the cytoplasmic surface of the endoplasmic reticulum. These findings and our previous investigations on the topography of seven enzymes of triacylglycerol, phosphatidylcholine and phosphatidylethanolamine biosynthesis (Ballas, L.M. and Bell, R.M., Biochim. Biophys. Acta 602, (1980) 578-590) indicate that the synthesis of the major cellular glycerolipids occurs asymmetrically on the cytoplasmic surface of the endoplasmic reticulum.
...
PMID:Topography of glycerolipid synthetic enzymes. Synthesis of phosphatidylserine, phosphatidylinositol and glycerolipid intermediates occurs on the cytoplasmic surface of rat liver microsomal vesicles. 627 Dec 31

A zymogen granule fraction has been isolated from rat pancreas, and its purity has been assessed by biochemical and morphological criteria. Specific activities of two marker enzymes, amylase and chymotrypsin, are increased by 4.6 and 5.4-fold, respectively, as compared to the homogenate. The purified fraction is devoid of detectable RNA, DNA and 5'-nucleotidase, glucose-6-phosphatase, and cytochrome c oxidase activities. Electron micrographs confirm the absence of mitochondria, lysosomes, and rough endoplasmic reticulum fragments. Zymogen granule membranes were isolated from this fraction on a sucrose gradient following lysis in alkaline buffer. Secretory contaminants were efficiently removed from the membranes as indicated by experiments in which labeled secretory proteins were added during the isolation procedure and secondly by measuring residual levels of amylase and chymotrypsin. Three enzyme activities were found in the membranes: thiamine pyrophosphatase, ATP-diphosphohydrolase, and low levels of acid phosphatase. Membrane proteins were solubilized by urea-Triton X-100 and separated in double-dimension (isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Isoelectric point and molecular weight of each protein band were determined.
...
PMID:Isolation of zymogen granules from rat pancreas and characterization of their membrane proteins. 629 Feb 20

We have found that opiate receptors in smooth microsomal fractions differ from synaptic membrane-associated receptors in proteolytic sensitivity. With 3 proteases of different substrate specificities (trypsin, chymotrypsin and S. griseus protease) smooth microsomal opiate receptors from rat brain were consistently less sensitive to limited proteolysis than were synaptic membrane receptors. Thiamine pyrophosphatase, a luminal Golgi membrane marker enzyme, exhibited a similar resistance to S. griseus protease in microsomal preparations, while microsomal Na+/K+-ATPase (ouabain-sensitive) was readily destroyed by trypsin. We also discovered that smooth microsomal opiate receptors co-migrate with both Golgi membrane and endoplasmic reticulum marker proteins on equilibrium density gradients under isopycnic conditions. Electron microscopic examination of the Golgi-enriched fraction showed the typical cisternae frequently associated with isolated Golgi membranes. Synaptic junctions, presynaptic membranes, myelin and mitochondria were conspicuously absent from this fraction. Since the microsomes isolated in vitro showed similar topography to those in vivo, the binding sites for opiates could be localized on the luminal surface membranes of the microsomal fractions. The exquisite sensitivity of synaptic membrane opiate receptors to proteolysis suggests that these receptors are found on the extracellular surface of the synaptic junction.
...
PMID:Microsomal opiate receptors differ from synaptic membrane receptors in proteolytic sensitivity. 629 19


<< Previous 1 2 3 4 5 Next >>

---