Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have asked whether treatment of normal cultured cells with proteases, other hydrolytic enzymes, or serum can convert them into transient phenocopies of transformed cells with respect to the very high rate of hexose transport characteristic of transformed cells. Treatment of density-inhibited cultures of normal chick embryo fibroblasts with trypsin, plasmin, neuraminidase, or hyaluronidase stimulated their rate of 2-deoxyglucose uptake to a level only marginally higher than that seen in normal exponentially growing cultures, and only 35-45% of that seen in transformed cultures. Addition of the hydrolytic enzymes to growing cell cultures had little effect on 2-deoxyglucose uptake. Serum, however, could stimulate 2-deoxyglucose uptake all the way up to the transformed level. Even though the hydrolases and serum differed in their ability to stimulate 2-deoxyglucose uptake, both reagents were capable of stimulating cell division equally well. Evidence is presented suggesting that the hexose transport rate is controlled by serum factors, and that proteolysis can affect the response of the cells of these factors.
 ...
PMID:Hydrolase and serum treatment of normal chick embryo cells: effects on hexose transport. 12 53

Dipolid human fibroblast-rich tissues contain a macromolecule with a molecular weight between 30,000 and 50,000 daltons which will inhibit the proliferation of fibroblasts in the G1 phase of the cell cycle (i.e., inhibit both 3H-thymidine uptake as well as the normal increase in cell number). The inhibitor is destroyed by trypsin but not by ribonuclease or deoxyribonuclease, and it is thermolabile. It has an acid IEP. It is not cytotoxic, and its inhibitory activity appears to be completely reversible. This fibroblast endogenous inhibitor does not interfere with the proliferation of DNA synthesis by human lymphocytes, bronchial carcinoma cells, or HeLa cells. The activity does not appear to be species specific. Therefore, we suggest that it is quite possible that the control of fibroblast proliferation resides in a fibroblast chalone. Diploid human fibroblasts, in contrast to chicken or mouse fibroblasts or heteroploid fibroblasts in general, stringently require serum for their proliferation. All of this mitogenic activity of calf serum can be concentrated in a molecular weight range around 100,000 daltons by ultrafiltration. All of the mitogenic activity within this molecular weight class can be concentrated at a pH of 5.2 via isoelectric focusing, and all of the activity at this isoelectric point can be concentrated in one peak on preparative polyacrylamide gel electrophoresis. This latter material is homogeneous at three different pH's in analytical gel electrophoresis as well as in SDS electrophoresis. This purified serum mitogen for diploid human fibroblasts in vitro also works in vivo and represents as much as 0.5% of calf serum protein, albeit there is much less of this protein in adult cow or horse. It is composed of two equal subunits weighing about 60,000 daltons each and contains about 2 moles of sialic acid, one S-S bond, and 6 moles of hexose per subunit. There is a reciprocal relationship between the biological activity of fibroblast inhibitor and serum mitogen, but there is no apparent direct interaction between these two proteins. Addition of pure serum mitogen to diploid human fibroblasts in vitro results in the release of commensurable chalone activity into the medium and a reciprocal loss of mitogen from the medium. Therefore, we propose that serum contains a single macromolecule which competes with endogenous chalone on the surface of diploid human fibroblasts and that this functions as an anti-chalone for the fibroblast.
 ...
PMID:Circulating factors controlling cell proliferation. 13 64

We have examined the role of proteolytic activity in the genesis and maintenance of the transformed phenotype by growing cultures of chick embryo fibroblasts transfromed by Rous sarcoma virus either in medium containing plasminogen-free serum or in medium to which protease inhibitors were added. Alterations in morphology, adhesiveness, and hexose transport were used as markers for the transformed state. Addition of the trypsin inhibitors NPGB or Soy Bean Trypsin Inhibitor at concentrations which inhibited transformation-associated fibrinolysis restored adhesiveness and morphology to near normal, but did not affect the rate of hexose transport. Growth of Rous-infected cells in plasminogen-free medium blocked the appearance of morphological and adhesive alterations, but allowed the rate of hexose transport to increase to the transformed level. Thus we were able to separate the appearance of transformation-specific changes in morphology and adhesiveness (which apparently require fibrinolytic activity) from the increased rate of hexose transport (which is independent of fibrinolytic activity). Another trypsin inhibitor, TLCK, although it did not inhibit fibrinolysis, was very effective at restoring adhesiveness and morphology as well as hexose transport to normal. This raises the possibility that there is another, perhaps earlier, protease involved in the genesis of the transformed phenotype.
 ...
PMID:Inhibition of protease activity in cultures of rous sarcoma virus-transformed cells: effect on the transformed phenotype. 16 81

The rate of hexose transport was compared in normal and virus-transformed cells on a monolayer and in suspension. It was shown that: 1) Both trypsin-removed cells and those suspended for an additional day in methyl cellulose had decreased rates of transport and lower available water space when compared with cells on a monolayer. Thus, cell shape affects the overall rate of hexose transport, especially at higher sugar concentrations. 2) Even in suspension, the initial transport rates remained higher in transformed cells with reference to normal cells. Scanning electron micrographs of normal and transformed chick cells revealed morphological differences only in the flat state. This indicates that the increased rate of hexose transport after transformation is not due to a difference in the shape of these cells on a monolayer.
 ...
PMID:Cell shape and hexose transport in normal and virus-transformed cells in culture. 19 15

Incubation of fat cells with insulin increased glycogen synthase I activity without changing total synthase activity. This effect of insulin was dependent upon the particular lot of albumin present in the medium and was abolished by incubating cells with trypsin. Half-maximal activation of glycogen synthase was obtained with 8 microunits/ml of insulin, a concentration very similar to that which half-maximally stimulated 3-O-methylglucose uptake. The basal percentage of phosphorylase a activity was not detectably altered by insulin, although it was decreased by incubating cells with 5 mM glucose. Insulin (50 microunits/ml) markedly opposed actions of epinephrine (0.05 to 10 muM) to increase phosphorylase a activity and decrease glycogen synthase I activity, effects which were observed without glucose. Partial activation of glycogen synthase by insulin was seen after 1 min and complete activation after 4 min. Glucose alone produced a transient increase in synthase I activity. When cells were incubated with insulin plus glucose for 4 min, the increase in the percent synthase I activity was much greater than the additive effects of insulin and glucose alone. This potentiation of the effect of insulin on glucogen synthase I activity depended on the time of incubation with glucose and on the concentration of the hexose. If cells were incubated with cytochalasin B before insulin plus glucose, the effect of glucose was abolished. These results suggest that there are at least two mechanisms by which insulin can increase fat cell glycogen synthase I activity. One requires glucose and activation occurs secondary to an increase in glucose transport; where another mechanism(s) is operative even in the absence of glucose.
 ...
PMID:Activation of rat adipocyte glycogen synthase by insulins. 40 14

The saturable insulin binding is linked to insulin degradation in two important target cells: The hepatocyte and the adipocyte. One of the consequences is that the changes in binding which are observed under various conditions cannot a priori be regarded as caused by either increased number of receptors or increased affinity of the binding site. This observation raises new questions. For instance, could the effect of insulin be mediated by a fragment of the molecule? No evidence which is available for the moment seems to rule out this hypothesis. The findings with insulin analogues, the kinetics of insulin binding and activation and the effect of mild trypsin treatment, would equally well support the hypothesis that the binding itself causes activation of hexose transport and that degradation secondary to binding mediates the activation.
 ...
PMID:[Insulin receptors (author's transl)]. 40 44

The effects of concanavalin A (Con A) and leucoagglutinin (LA) on the locomotor response of phagocytes have been studied in vitro. At concentrations of 1 to 4 microgram/mol, Con A and LA induced maximal chemokinesis and chemotaxis of monocytes, macrophages and, to a lesser degree, also of neutrophils. The lectin-induced locomotion was accompanied by membrane alterations and metabolic changes, as shown by an increase of the 3H-uridine uptake and a rise of the hexose monophosphate shunt activity. The chemotactic activity of Con A was inhibited by alpha-methyl mannoside (50 mM) or by pretreatment of the cells with trypsin. These data indicate that lectins such as Con A induce chemotaxis by a specific binding to receptors of the cell membrane. It is suggested that bivalent ligand binding is required as a signal to elicit chemotactic locomotion.
 ...
PMID:Chemotactic activity of lectins in vitro. 64 77

An inhibitor of papain and other SH-proteases was purified 520-fold from human epidermis extracts by acetone fractionation, heat treatment, papain-Sepharose affinity chromatography, and Sephadex G-50 chromatography. The purified inhibitor had a molecular weight of 12,600 and contained no hexose, as tested by the anthrone reaction. The inhibitor survived in a boiling water bath, in 5% trichloroacetic acid, 20 mM Na3PO4 (pH 12.1) and 4 M NH4OH (pH 11.9). By isoelectric focusing 2 major activity peaks with pI's of 4.6 and 4.8, and a minor peak with a pI of 4.9 was fractioned, and 3 corresponding protein bands were seen after analytical isoelectric focusing. Immunization of rabbits with the purified inhibitor yielded a highly specific anti-inhibitor serum. The purified inhibitor inhibited papain, ficin, human cathepsins B and C, and slightly inhibited bromelain. No inhibition of serine proteases (bovine trypsin and chymotrypsin A, porcine elastase) or an acid protease (human cathepsin D) was observed. Evidence was obtained that the inhibitor formed a complex with both dithiothreitol-activated papain and enzymatically inactive mercuripapain.
 ...
PMID:Purification and some characteristics of the human epidermal SH-protease inhibitor. 68 77

The nature of the acceptors for activated C3 present on immunoglobulins was studied by using the fixation of C3 to Sepharose beads after activation with trypsin as a model system. C3 fixation to Sepharose is a property exclusively linked to the short active state of C3. This binding could be inhibited by various carbohydrates and their affinity for C3 was calculated from the extent of the inhibition of the binding of C3 to Sepharose. Mono-, di-tri- and tetrasaccharides showed on a molar basis an increasing but still weak affinity for active C3. The C3 fixation of Sepharose could be inhibited by immunoglobulins and the degree of inhibition was proportional to the hexose content of the immunoglobulin preparations. The isolated polysaccharide moiety of IgG gave the same inhibition as the intact IgG. In addition cell wall polysaccharides of Salmonella abortus equi were found to have a high affinity for active C3. Thus, the more complex polysaccharides such as those present on immunoglobulins and cell walls might function as acceptor for activated C3.
 ...
PMID:The binding of activated C3 to polysaccharides and immunoglobulins. 72 84

Transport of D-[3H]deoxyglucose and D-[3H]glucose by purified fat cell plasma membranes was markedly inhibited by cytochalasin B,dipyridamole, or phlorizin. The rate of L-[3H]glucose uptake was significantly slower and was unaffected by cytochalasin B. Both the rates of association of [3H]cytochalasin B with the fat cell plasma membrane and its dissociation from the membrane was significantly enhanced by the presence of Ca2+ or Mg2+. Scatchard plot analysis of [3H]cytochalasin B binding to fat cell membranes indicated the presence of high affinity and low affinity sites which exhibited apparent dissociation constants of about 6 X 10(-7) M and 5 X 10(-6) M, respectively. The concentration of cytochalasin B which half-maximally inhibited D-glucose transport was about 5 X 10(-7) M, indicating the high affinity sites are involved in transport inhibition. D-Glucose at concentrations as high as 100 mM had no effect on the binding of [3H]cytochalasin B to these high affinity sites, while the transport inhibitors phlorizin, phloretin, and dipyridamole markedly inhibited this binding. The protein reagents N-ethylmaleimide, 2-hydroxy-5-nitrobenzylbromide, 1-fluoro-2,4-dinitrobenzene, dithiothreitol, and trypsin also reduced binding. Extracted fat cell plasma membrane lipids dispersed by sonication did not bind [3H]cytochalasin B nor take up glucose by a cytochalasin B-sensitive pathway. The results indicate that cytochalasin B inhibits hexose transport in fat cells secondary to its interaction with membrane protein sites distinct from those which bind D-glucose.
 ...
PMID:Characterization of (3H)cytochalasin B binding to the fat cell plasma membrane. 81 83


1 2 3 4 5 6 Next >>