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

The layer of mucosubstance that is associated with the free surface membranes of the pneumonocytes in the lungs of the toad Xenopus laevis and the lizard Lacerta viridis was demonstrated by electron microscopy using iron oxide stain. The form and staining reactions of the mucosubstance layer were similar in both animals. In electron micrographs the mucosubstance was represented by a band of densely stained material (25-50 nm thick) which coated the entire free surface of the pneumonocytes. It appeared to be firmly attached to the outer leaflet of the superficial plasma membrane. Short lengths of osmiophilic membranes, presumed to be fragments of pulmonary surfactant, were often observed lying free in the air spaces but they did not show any affinity for iron stain. Incubation of lung sections in a solution of neuraminidase produced a marked decrease in the intensity of the surface staining; no change was detected after incubation in trypsin, papain, hyaluronidase, N-acetyl cysteine, or phosphate buffer. It is, therefore, concluded that the pneumonocyte surface coat consists mainly of a sialomucin.
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PMID:The mucosubstance coating the pneumonocytes in the lungs of Xenopus laevis and Lacerta viridis. 16 63

We have perfused isolated rat livers with hypocalcemic (4.4 mg 100 ml) Krebs-Ringer bicarbonate albumin buffer. After 15 min of perfusion, a substance appeared in the perfusate which decreased rat renal adenylate cyclase activation by parathyroid hormone (PTH). The material in the perfusate was purified greater than 50,000-fold by Bio-Gel P-10 chromatography. The purified antagonist decreased the activation of rat renal cortical adenylate cyclase by PTH, glucagon, and epinephrine 75 to 100%. Concentration response curves for each of the hormones indicated a noncompetitive interaction of the inhibitor with the hormone. The inhibition was not species-specific, as the activation of the parathyroid hormone-responsive adenylate cyclase in cat renal cortex was also abolished by the inhibitor from the perfused rat liver. The inhibitor is a peptide, Mr equal to similar to 1000, which is heat-stable, acid-stable, alkai-labile, and is destroyed by trypsin, leucine aminopeptidase, and elastase. It is not destroyed by phosphodiesterase, 5'-nucleotidase, alkaline phosphatase, neuraminidase, RNase, or phospholipase A. The inhibitor is not produced by isolated rat livers perfused with normocalcemic perfusion media. It is unclear whether the peptide is synthesized by the liver or whether it is a breakdown product of a larger peptide or protein in the liver. This is the first reported peptide inhibitor of adenylate cyclase.
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PMID:Isolation of a unique peptide inhibitor of hormone-responsive adenylate cyclase. 16 24

The insulin or proinsulin response of the isolated rat adipocyte was destroyed by preincubation with trypsin. After 120 minutes, biological responsiveness partially regenerated. Similarly, the biological responsiveness of the isolated fat cell to non-suppressible insulin-like activity (NSILA) was only partially destroyed following trypsin digestion, and did not regenerate. In contrast to the above, cyclic AMP or dibutyryl cyclic AMP effects were unaltered by trypsin or neuraminidase digestion.
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PMID:Studies of the biological activity of insulin, cyclic nucleotides and concanavalin A in the isolated fat cell. 16 39

The ascites form of a chemically induced guinea pig hepatoma, line-10, was resistant to killing in vitro by xenogeneic antibody and guinea pig complement. Pretreatment of line-10 cells with certain proteolytic enzymes rendered tham susceptible to the killing action of antibody and guinea pig complement. The effects of enzyme pretreatment were dependent on enzyme concentration, temperature, and could be blocked by addition of competitive or non-competitive inhibitors. The effect of the enzyme treatment could reversed by incubating the treated cells at 37 degrees C (but not at 0 degrees C), in the absence of the enzyme. Effective enzymes included ficin, bromelain, pronase, elastase, papain, trypsin, collagenase, lipases type I and type VI, and the neuraminidase preparation isolated from Clostridium perfringens. The activity of the lipase preparations and the neuraminidase preparation isolated from Clostridium perfringens appeared to be caused by proteolytic enzyme contamination. Enzyme preparations that proved ineffecitve in rendering the line-10 cells sensitive to killing by antibody and guinea pig complement included DNase, RNase, beta-glucuronidase type 6A or type B10, hyaluronidase type V or type VI, and pectinesterase.
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PMID:Lysis of tumor cells by antibody and complement. VI. Enhanced killing of enzyme-pretreated tumor cells. 17 70

Studies have been conducted to characterize further the interaction between 125I-labeled bovine thyrotropin (TSH) and bovine thyroid plasma membranes. Sequential subcellular fractionation of thyroid homogenates yielded preparations of progressively greater specific binding activity, highest activity being found in fractions previously shown to contain predominately plasma membranes (Amir, S. M., Carraway, T.F., Kohn, L.D., and Winand, R.J. (1973) J. Biol. Chem. 248, 4092-4100). Although binding of 125I-TSH by plasma membranes was greatest at pH 6.0, studies were conducted at pH 7.45 as well as pH 6.0, and results obtained differed quantitatively, but not qualitatively. Binding was maximal at 0 degrees, 15 degrees, and 22 degrees and steady state values remained unchanged for at least 22 hours. At 37 degrees, binding was decreased by 40% at 1 hour; the loss was even greater (65%) at 50 degrees. A similar loss of binding was evident when membranes were preincubated without TSH at 37 degrees or higher and were then incubated with 125I-TSH at 0 degrees. Lineweaver-Burk analysis indicated that preincubation resulted in loss of receptor sites without change in affinity of residual receptors. Addition of Ca2+ (1 to 10 mM) to the preincubation medium prevented the effect of preincubation at 37 degrees by preserving the number of receptor sites without altering their affinity. Under similar conditions, Na+ and K+ were without protective effect. Membranes bound 45Ca2+ in a specific and saturable manner. Scatchard plots indicated a dissociatiion constant (Kd) of 9 X 10(-5) M and a capacity (n) of 54 nmol/mg of membrane protein. 45Ca2+ was also displaced from membranes by Mg2+ and Mn2+. Ca2+ had a biphasic effect on binding; low concentrations (1 to 10 muM) added to the incubation mixture stimulated binding, while higher concentrations (0.1 mM) caused inhibition. Mg2+ and Mn2+, at comparable concentrations, were also inhibitory, Na+ and K+ less so. In the case of Ca2+, both the stimulatory and inhibitory concentrations were lower than those required to achieve saturation of Ca2+-binding sites. Proteolytic enzymes (trypsin, alpha-chymotrypsin, and pronase) sharply reduced binding of 125I-TSH, owing to a decrease in receptor sites. Phospholipases A and C enhanced binding of TSH, while neuraminidase and beta-galactosidase were without measurable effect.
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PMID:Properties of the interaction between bovine thyrotropin and bovine thyroid plasma membranes. 18 81

Guinea-pig melanocytes in mixed epidermal cell cultures bind melanocyte-stimulating hormone in a distinct focal surface area in their perinuclear field and thus follow the same pattern previously described for Cloudman melanoma cells. The labeling index ranged from 18 to 34%. Pretreatment of cultures with trypsin leads to destruction of melanocyte-stimulating hormone receptors whereas neuraminidase has no such effect.
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PMID:Melanocyte-stimulating hormone receptors on cultured guinea-pig melanocytes. 18 12

Surface antigens of HeLaHVJ cells, a cell line persistently infected with HVJ, were studied by fluorescent antibody staining. After absorption with concentrated HVJ virions and HeLa cells, anti-HeLaHVJ antiserum was able to demonstrate specific surface fluorescence on HeLaHVJ cells, while this serum no longer reacted with original HeLa cells nor with HVJ virions. During cytolytic infection of HeLa cells with HVJ, this specific surface antigen appeared at an early stage of infection prior to the appearance of newly synthesized HVJ viral antigens and moreover appeared in spite of the inhibition of viral protein synthesis. This antigen was detected neither on HeLa cells infected with other myxoviruses except HVJ nor on various other kinds of cells infected with HVJ. The specific surface antigen was still found on the HeLaHVJ cell surface after incubation at 38 degrees C for two days, while HVJ structural antigens on the cell surface no longer could be detected. Mild short-term treatment of HeLa cells with trypsin, neuraminidase from vibrio cholerae, phospholipase-C and hyaluronidase failed to expose specific antigen. The antigen was distinguishable from the Forssman and human blood type antigens. The mechanism of appearance of a new antigen on the surface of HeLaHVJ cells remains unclear.
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PMID:Surface antigens on HeLa cells persistently infected with HVJ (Sendai virus). 18 62

The radioactive 125I-labelled neurotoxin of C. botulinum type A, when incubated with rat brain homogenate, is bound selectively to the synaptosome fraction. Intact toxin was liberated from the synaptosome fraction by treatment with Triton X-100, SDS, trypsin or neuraminidase.
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PMID:Binding of botulinum neurotoxin to the synaptosome fraction of rat brain. 18 22

125I-angiotensin II (AII) specifically bound to rat glomerular basement membrane (GBM). The kinetics of binding were similar to those obtained with the total glomeruli. The apparent dissociation constant was close to 50 pM with both preparations. The number of sites related to the amount of protein was two times greater with GBM than with total glomeruli. Since the amount of GBM protein extracted from a given amount of glomerular protein was about 10%, it was possible to estimate the share of the GBM binding sites for AII as representing 20% of the total number present in the entire glomerulus. Binding studies at equilibrium as a function of 125I-AII concentration and competitive binding experiments suggested either multiplicity of the binding sites or cooperativity in the binding reaction. Degradation of 125I-AII in the presence of GBM was slight and did not increase with time. The difference in the degrees of degradation of 125I-AII was too small to account for the observed difference in binding when the results obtained with GBM and isolated glomeruli preparations were compared. 125I-AII binding to GBM was increased after treatment of these membranes with collagenase, slightly diminished with neuraminidase, and almost completely abolished with trypsin suggesting the proteic nature of the receptor. 125I-AII binding to GBM was diminished after incubation of GBM with anti-GBM antibodies as a result of a decrease in the number of binding sites. 125I-AII binding was even more diminished in preparations of glomeruli isolated from rats passively immunized with anti-GBM antibodies when compared with glomeruli from control animals. This resulted from both smaller affinity for AII and decrease in the number of the binding sites. The present data provides evidence for specific binding sites for AII localized on GBM. This is noteworthy since receptors for polypeptide hormones are currently observed on the surface of cell membranes. These findings also suggest a new physiological role for AII which might involve modification of GBM permeability.
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PMID:High affinity binding of 125I-angiotensin II to rat glomerular basement membranes. 18 23

Further investigation with the inhibitor of interferon activity (IME) isolated from mouse embryo tissue is reported. The present results bring some new data concerning the physiochemical properties of the interferon antagonist. It is not dialysable, not sensitive to trypsin, lysozyme, hyaluronidase, RNAse and pH 2, but is sensitive to pH 10 and neuraminidase. Concentrated and partly purified tissue antagonist of interferon was separated on a column with Sephadex G 100. Three distinct, well separated fractions showing antiinterferon activity were obtained. The characteristics and molecular weight of each of these fractions were determined.
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PMID:Physicochemical characteristics of IME-inhibitor of interferon activity from mouse embryo tissues. 20 16


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