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

Matrix-free cells from chick-embryo sterna were incubated with various concentrations of 2,2'-bipyridyl, an iron chelator that inhibits prolyl hydroxylase and lysyl hydroxylase. At concentrations in the region of 0.1 mM, significant effects on cartilage collagen hydroxylation and secretion were observed. When the underhydroxylated collagens were subsequently digested with chymotrypsin or chymotrypsin plus trypsin at 4 degrees C for 15 min, the minor cartilage collagen precursors (namely types IX and XI) were extensively degraded; type II procollagen was only partially susceptible and was converted into underhydroxylated collagen. The results demonstrate that there were significant differences in triple-helix stability among cartilage collagens such that the underhydroxylated minor collagen precursors were unable to attain a native structure under conditions where type II procollagen was successful.
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PMID:Underhydroxylated minor cartilage collagen precursors cannot form stable triple helices. 335 24

Ribonucleotide reductase catalyzes the rate-limiting step in the formation of 2'-deoxyribonucleoside 5'-triphosphates. It consists of two nonidentical protein subunits, the nonheme iron subunit, and the effector-binding subunit. It has previously been shown that these two components making up the active enzyme species are not coordinately synthesized or degraded. It was found that the effector-binding subunit was more sensitive to proteolysis by chymotrypsin, to heating at 55 degrees C, and to the sulfhydryl reagents, pCMB and NEM. The nonheme iron subunit was more sensitive to trypsin treatment. ATP and dATP protected the effector-binding subunit from proteolytic inactivation. Neither ATP nor CDP protected the effector-binding subunit from inactivation by the sulfhydryl reagents. These data indicate that the protein properties of the two subunits of mammalian ribonucleotide reductase are significantly different.
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PMID:Differential sensitivities of the subunits of mammalian ribonucleotide reductase to proteases, sulfhydryl reagents, and heat. 351 48

Ribonucleotide reductase catalyzes the critical reaction in which the deoxyribonucleotides required for DNA replication are synthesized de novo. This enzyme consists of two non-identical protein subunits, both of which are required for enzymatic activity. These subunits consist of a non-heme iron and an effector-binding subunit. These subunits are not coordinately regulated as the cells pass from G1 to the S phase of the cell cycle. Studies carried out with the holoenzyme and the isolated subunits indicate that the effector-binding subunit is more susceptible to chymotrypsin and the sulfhydryl reagents, pCMB and NEM, than is the non-heme iron subunit. The non-heme iron subunit is more susceptible to trypsin than is the effector-binding subunit. The presence of ATP or dATP protects the effector-binding subunit from proteolysis by either trypsin or chymotrypsin. The loss of activity in the holoenzyme, as a result of proteolysis, parallels the loss of the particular subunit. These results demonstrate that the protein properties of the subunits are significantly different to account for the differential turnover. The binding of nucleotides to the effector-binding site(s), which in turn regulates ribonucleotide reductase activity, is very specific. Formycin 5'-triphosphate and etheno-ATP could not replace ATP in the CDP reductase reaction. 2',3'-DideoxyATP was 5-fold less active than dATP as a negative effector; etheno-dATP was not inhibitory. AraGTP and BuPdGTP could not replace dGTP as a positive effector of ADP reduction. BuPdGTP, but not araGTP, served as an inhibitor of CDP reduction. 2',3'-DideoxyTTP was much less active as either an activator of GDP reduction or an inhibitor of ADP reduction. These studies indicate that the binding to the allosteric sites is highly specific and suggest that the structural requirements for the binding of activators are different from the structural requirements for the binding of inhibitors.
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PMID:Protein properties of the subunits of ribonucleotide reductase and the specificity of the allosteric site(s). 354 6

1. Iron was added to hen ovotransferrin to 30% saturation and the protein was digested with trypsin or chymotrypsin. 2. Iron-binding fragments were isolated. They carried one atom of iron/mol (mol.wt. 35000) and consisted of a single polypeptide chain derived from the N-terminal half of the protein. Carbohydrate was not present. 3. The fragments were able to bind a variety of metals and to donate iron to reticulocytes.
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PMID:The formation of iron-binding fragments of hen ovotransferrin by limited proteolysis. 446 61

Rat embryo parietal yolk sacs synthesized and secreted underhydroxylated [14C]proline-labeled basement membrane procollagen when incubated in the presence of the iron chelator alpha,alpha'-dipyridyl and [14C]proline. Upon reduction and sodium dodecyl sulfate-agarose gel filtration, this procollagen eluted as a discrete peak of labeled material close to the position of the beta components of type I collagen. Secreted underhydroxylated procollagen contained interchain disulfide bonds and was completely degraded by a 6 hr treatment with alpha-chymotrypsin at 4 degrees C. Results from 4 hr incubations indicated that the distribution of 14C-procollagen between tissue and medium was unaffected by the presence of alpha,alpha'-dipyridyl, but analysis of results from pulse-label and chase experiments revealed that underhydroxylated procollagen was secreted at less than half the rate of control procollagen.
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PMID:Studies on the underhydroxylated basement membrane procollagen synthesized by rat parietal yolk sacs in the presence of alpha,alpha'-dipydridyl. 621 58

Complex III was isolated and purified from bakers' yeast by ammonium sulfate fractionation and column chromatography on Ultrogel AcA 34. The purified complex contained 7.03 nmol/mg of protein and 4.24 nmol/mg of protein of cytochromes b and c1, respectively. The specific activity of the complex was 17.1 mumol/min/mg of protein, using the decyl analog of coenzyme Q as substrate. Electrophoresis of the purified complex revealed the presence of seven polypeptides with molecular weights ranging from 15,500 to 50,000. Polypeptides having molecular weights lower than 15,000 were not observed, except when the complex was dissociated in the absence of proteolytic inhibitors, suggesting that these low molecular weight species arise as a result of proteolytic digestion of the complex. The isoelectric points of the subunits of complex III and their stoichiometry wee determined. Trypsin and chymotrypsin digestion of the oxidized and reduced forms of the isolated complex suggested that the two high molecular weight core proteins are embedded within the complex and hence are inaccessible to the exogenous proteases, while cytochromes b and c1, the iron-sulfur protein, and the 17,500-dalton subunit are substantially exposed to the surface of the complex. The iron-sulfur protein appears to undergo a conformational change upon reduction of the complex, rendering it less susceptible to trypsin digestion. The core proteins and the iron-sulfur protein were purified, and antibodies against these proteins were raised. Immunoinhibition studies with these antibodies also indicated that the antigenic sites of the core proteins were embedded in the complex.
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PMID:Purification and polypeptide characterization of complex III from yeast mitochondria. 628 57

The orientation of the different subunits of complex III in the yeast inner mitochondrial membrane has been investigated by several different approaches. Immunoinhibition studies of cytochrome c reductase activity in intact mitoplasts and submitochondrial particles using IgG obtained from specific antisera against complex III, the iron-sulfur protein, core protein I, and core protein II suggested a transmembranous orientation of the complex with the antigenic sites of the iron-sulfur protein exposed on the cytoplasmic surface of the membrane. A lack of immunoinhibition was observed with the IgG against either core protein suggesting that these proteins may not be involved in catalysis. Digestion of mitoplasts with chymotrypsin indicated that the protein mass of cytochromes b and c1 protrudes from the cytoplasmic surface of the membrane; however, the hemes of cytochrome b appear to be buried within the membrane while the heme of cytochrome c1 is partially exposed on the chymotrypsin-sensitive portion of the polypeptide. By contrast, the iron-sulfur protein does not protrude from the membrane as it is completely resistant to chymotrypsin digestion. Labeling with the hydrophilic membrane-impermeant probe diazobenzenesulfonate suggests that core protein II is exposed on both sides of the membrane but protrudes into the matrix; while core protein I is within the membrane. Immunoprecipitation studies of sodium dodecyl sulfate and Triton X-100-solubilized mitochondria with subunit-specific antisera suggest that cytochromes b and c1 and core protein I are tightly associated in complex III. By contrast, the iron-sulfur protein and core protein II are loosely associated with the other subunits of the complex such that they are dissociated by low concentrations of detergent.
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PMID:Topographical orientation of complex III in the yeast mitochondrial membrane. 631 51

The susceptibility of lactoferrin in bovine colostrum and human milk to digestion by trypsin and chymotrypsin has been investigated. Neither enzyme had much effect on the lactoferrin-mediated antimicrobial activity of human milk, and the iron binding capacity of lactoferrin in the milk was only slightly reduced. Likewise both enzymes had only a slight effect on the iron-binding capacity of purified lactoferrin. Although iron-free (apo)lactoferrin was slightly more susceptible to digestion, especially by chymotrypsin, than the iron-saturated form, the difference was much less than has been found in earlier studies with other proteins of the transferrin class. In contrast, trypsin destroyed the antimicrobial activity of bovine colostrum, and, in line with earlier studies, appreciably reduced the iron-binding capacity of both colostrum and purified bovine apolactoferrin. Bovine iron-saturated lactoferrin was more resistant to digestion. The unusual resistance of human apolactoferrin to proteolysis may reflect an evolutionary development designed to permit its survival in the gut of the infant.
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PMID:The effect of trypsin and chymotrypsin on the in vitro antimicrobial and iron-binding properties of lactoferrin in human milk and bovine colostrum. Unusual resistance of human apolactoferrin to proteolytic digestion. 634 99

After discussing the psychological importance of the problem, the author stresses that the best treatment of pigmentations after sclerosis is prevention, based on experience and faultless technique (careful choice of sclerosants, local compression, evacuation of thrombi). The author then briefly reviews the pathophysiology of melanin dyschromias and their causes and presents the histological finding of a mixed origin for post-sclerosis pigmentations (melanin and iron). Various attempts at treatment are presented. The most effective form of treatment seems to be the percutaneous application of a mixture consisting of : -an iron chelator (desferoxamine), -an anti-inflammatory (alpha-chymotrypsin), -an anti-melanin agent (mequinol).
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PMID:[Pigmentation following sclerosis]. 665 50

Acidic isoferritins have been identified as leukemia-associated inhibitory activity (LIA), which suppresses colony and cluster formation of colony-forming unit-granulocyte macrophages from normal donors but not from patients with leukemia. LIA was detected in all ferritin preparations tested, including ferritin isolated from normal heart, spleen, liver, and placental tissues, and from the spleens of patients with chronic myelogenous leukemia and Hodgkin's disease. Purified preparations of LIA were composed almost entirely of acidic isoferritins, as determined by immunoassay, radioimmunoassay, and isoelectric focusing. The inhibitory activity in the LIA and ferritin samples was inactivated by a battery of antisera specific for ferritin, including those prepared against acidic isoferritins from normal heart and spleen tissues from patients with Hodgkin's disease, and those previously absorbed with basic isoferritins. Antisera absorbed with acidic isoferritins did not inactivate the inhibitory activity. Separation of LIA and chronic myelogenous leukemia and normal spleen ferritin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing confirmed that the regions of peak inhibitory activity corresponded in each to an apparent molecular weight of approximately 550,000 and to a pI value of 4.7. Similar physicochemical characteristics included inactivation by methods that dissociate ferritin molecules into subunits and by treatment with trypsin, chymotrypsin, pronase, and periodate. The purified preparations were extremely stable to heat treatment. The glycoprotein nature of the inhibitory activity was substantiated because it bound to concanavalin A-Sepharose and was eluted off by alpha-methyl mannose. Inhibitory activity of the activity of the acidic isoferritins was detected at concentrations as low as 10(-17)-10(-19) M and iron saturation did not appear to be necessary for its action. These results implicate acidic isoferritins in the regulation of normal myelopoiesis and suggest a role for them in the progression of leukemia.
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PMID:Identification of leukemia-associated inhibitory activity as acidic isoferritins. A regulatory role for acidic isoferritins in the production of granulocytes and macrophages. 697 99


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