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)

Peptide YY (PYY) and neuropeptide Y (NPY) inhibit agonist-induced adenosine 3',5'-cyclic monophosphate (cAMP) production and pepsinogen secretion from chief cells. We used radiolabeled PYY and NPY to characterize receptors on chief cells from guinea pig stomach. Binding of 125I-labeled PYY was rapid (70% maximal within 10 min) and specific (not inhibited by secretin, vasoactive intestinal peptide, cholecystokinin, carbachol, prostaglandin E2, forskolin, or cholera toxin). Measurement of the ability of PYY to inhibit binding of 125I-PYY indicated the presence of 1.8 x 10(3) high-affinity [dissociation constant (Kd) = 1.7 nM] and 5.1 x 10(4) low-affinity (Kd = 83.3 nM) sites/cell. Internalization of bound 125I-PYY was suggested by slow and incomplete dissociation in the presence of unlabeled PYY (50% after 2 h) and was examined further by measuring residual binding after washing with acetic acid (pH 2.5), glycine (pH 10.5), or trypsin. After 30 min at 37 degrees C, internalization of radioligand was evidenced by the failure of washing with these solutions to remove 50-65% of bound radioactivity. At 4 degrees C, internalization of 125I-PYY was nearly abolished. Binding of 125I-PYY and 125I-NPY was inhibited by NPY-(13-36) but not by [Leu31,Pro34]NPY indicating that these are Y2 receptors. In guinea pig chief cells, PYY and NPY modulate cAMP-mediated pepsinogen secretion by interacting with specific high-affinity Y2 receptors.
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PMID:Y2 receptors for peptide YY and neuropeptide Y on dispersed chief cells from guinea pig stomach. 131 99

The human erythroleukemia cell line (HEL) has been used as a model system for studying signal transduction processes as they might relate to platelet/megakaryocyte function. We were interested in examining the role of thrombin in the regulation of adenylyl cyclase in this cell line. As opposed to its predominantly inhibitory effects on cyclic AMP production in platelets or in membranes from HEL cells, our initial experiments in intact HEL cells revealed that thrombin markedly potentiated the cyclic AMP response to prostaglandin E1 (2.9 +/- 0.2-fold), prostacyclin (1.9 +/- 0.2-fold) and carbacyclin (2.5 +/- 0.5-fold), measured either by radioimmunoassay or by the [3H]adenine preloading procedure. Thrombin, although ineffective alone, also potentiated cyclic AMP production stimulated by vasoactive intestinal peptide (1.6 +/- 0.2-fold), cholera toxin (3.0 +/- 0.6-fold) and AIF4- (2.3 +/- 0.6-fold), but not by forskolin (0.9 +/- 0.1-fold). The thrombin effect 1) produced an increase in the efficacy of the prostaglandins with no change in potency; 2) was long-lived; 3) required the proteolytic activity of thrombin; 4) was insensitive to pertussis toxin; and 5) was at least partially mimicked by trypsin, extracellular ATP and UTP, platelet activating factor and activators of protein kinase C. Down-regulation of protein kinase C or pre-exposure to the protein kinase inhibitor staurosporine blocked the potentiating effect. Together, these results suggest that in HEL cells, the mechanism of thrombin potentiation of cyclic AMP production may involve alterations in the interaction between stimulatory guanine nucleotide binding protein and the catalytic subunit of adenylyl cyclase, possibly involving protein kinase C-mediated phosphorylation.
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PMID:Potentiation of cyclic adenosine monophosphate production by thrombin in the human erythroleukemia cell line, HEL. 133 12

A study was made with different doses of cerulein (2, 4, 10 and 20 micrograms/kg) administered subcutaneously to rats by four injections at intervals of 1 hr; the aim of this work was to study exocrine pancreatic secretion of the rat under cerulein-induced acute pancreatitis, analyzing enzyme and hydroelectrolyte secretion of pancreatic juice. A further aim was to study the relationship between the dose of cerulein and the plasma levels of peptides controlling hydroelectrolyte secretion of the pancreas, like secretin and vasoactive intestinal peptide (VIP). At the lowest dose schedule, the amounts of total protein and enzymes (amylase and trypsin) in pancreatic juice decreased significantly, plasma amylase increased, and the pancreas became edematous. Higher doses magnified these effects. By contrast, ductular function (flow and HCO3-) was well preserved in cerulein-treated rats, and this was probably due to the significant increase in plasma levels of immunoreactive secretin whereas VIP levels were unchanged. The secretin released by treatment with cerulein is able to palliate the lack of flow from acinar origin that is affected in the process of acute pancreatitis, being a beneficial response to the cerulein treatment.
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PMID:Cerulein-induced acute pancreatitis in the rat. Study of pancreatic secretion and plasma VIP and secretin levels. 137 Sep 34

A vasoactive intestinal peptide (VIP)-binding protein purified from guinea pig lung membranes (p18) was digested with trypsin, and the amino acid sequence of the peptide fragments was determined. The sequence of six tryptic fragments of p18 was identical with subsequences present in mammalian calmodulin. Authentic porcine brain calmodulin and p18 co-migrated on an sodium dodecyl sulfate-electrophoresis gel and displayed identical chromatographic behavior on a reverse phase high performance liquid chromatography column. The VIP-binding properties of p18 and calmodulin were indistinguishable. Both proteins displayed saturable and apparent high affinity binding of VIP, evidenced by potent inhibition of complexation with [Tyr10-125I]VIP by unlabeled VIP (IC50 = 6.0-8.1 nM). Rat growth hormone releasing factor and a C terminally extended form of VIP ([Leu17]VIP-GKR) also displayed potent inhibition of the binding (IC50 = 6.4 and 4 nM, respectively). These neuropeptides are potential modulators of calmodulin function.
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PMID:Identity of a membrane-bound vasoactive intestinal peptide-binding protein with calmodulin. 152 80

Several lines of evidence suggest a possible role for mast cell proteases in modulating the biologic effects of neuropeptides. To explore the potential of such interactions in human airway, we examined the activity of human tryptase, the major secretory protease of human lung mast cells, against several neuropeptides with proposed regulatory functions in human airway. Using highly purified tryptase obtained from extracts of human lung, we determined the sites and rats of hydrolysis of vasoactive intestinal peptide (VIP), peptide histidine-methionine (PHM), calcitonin gene-related peptide (CGRP), and the tachykinins substance P (SP), neurokinin A (NKA), and neurokinin B (NKB). Tryptase hydrolyzes VIP rapidly at several sites (Arg12, Arg14, Lys20, and Lys21) with an overall kcat/Km of 1.5 x 10(5) M-1 s-1 and hydrolyzes PHM primarily at a single site (Lys20) with a kcat/Km of 1.9 x 10(4) M-1 s-1. Tryptase also rapidly hydrolyzes CGRP at two sites (Arg18 and Lys24) with a kcat/Km of 2.7 x 10(5) M-1 s-1. The tachykinins are not hydrolyzed by tryptase. These observations raise the possibility that tryptase-mediated degradation of the bronchodilators VIP and PHM combined with exaggerated mast cell release of tryptase may contribute to the increase in bronchial responsiveness and the decrease in immunoreactive VIP in airway nerves associated with asthma. The favorable rates of hydrolysis of CGRP suggest that tryptase may also terminate the effects of CGRP on bronchial and vascular smooth muscle tone and permeability.
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PMID:Degradation of airway neuropeptides by human lung tryptase. 169 72

The processing of proenkephalin was studied using [35S]methionine pulse-chase techniques in primary cultures of bovine adrenal medullary chromaffin cells. Following radiolabeling, proenkephalin-derived peptides were extracted from the cells and separated by reverse-phase HPLC. Fractions containing proenkephalin fragments were digested with trypsin and carboxypeptidase B to liberate Met-enkephalin sequences and subjected to a second HPLC step to demonstrate association of radiolabel with Met-enkephalin. Processing of proenkephalin is complete within 2 h of synthesis, suggesting completion at or soon after incorporation into storage vesicles. Pretreatment of the cells with nicotine, histamine, or vasoactive intestinal peptide to enhance the rate of proenkephalin synthesis failed to alter the time course of processing and had minimal effects on the distribution of products formed. Addition of tetrabenazine, an inhibitor of catecholamine uptake into chromaffin vesicles, during radiolabeling and a 6-h chase period caused enhanced proenkephalin processing. These results suggest that the full range of proenkephalin fragments normally found in the adrenal medulla (up to 23.3 kDa) represents final processing products of the tissue and that termination of processing may depend on the co-storage of catecholamines.
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PMID:Processing of proenkephalin in adrenal chromaffin cells. 186 Nov 55

The sympathetic innervation of rat sweat glands undergoes a target-induced switch from a noradrenergic to a cholinergic and peptidergic phenotype during development. Treatment of cultured sympathetic neurons with sweat gland extracts mimics many of the changes seen in vivo. Extracts induce choline acetyltransferase activity and vasoactive intestinal peptide expression in the neurons in a dose-dependent fashion while reducing catecholaminergic properties and neuropeptide Y. The cholinergic differentiation activity appears in developing glands of postnatal day 5 rats and is maintained in adult glands. It is a heat-labile, trypsin-sensitive, acidic protein that does not bind to heparin-agarose. Immunoprecipitation experiments with an antiserum directed against an N-terminal peptide of a cholinergic differentiation factor (CDF/LIF) from heart cells suggest that the sweat gland differentiation factor is not CDF/LIF. The sweat gland activity is a likely candidate for mediating the target-directed change in sympathetic neurotransmitter function observed in vivo.
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PMID:Characterization of a target-derived neuronal cholinergic differentiation factor. 198 70

The synthesis of proenkephalin was assessed in primary cultures of bovine adrenal medullary chromaffin cells by incubation of the cells with [35S]methionine, digestion of proenkephalin-derived peptides with trypsin and carboxy-peptidase B, and quantitation of radioactivity incorporated into Met-enkephalin following reversed-phase HPLC. Nicotine, histamine, and vasoactive intestinal peptide each enhanced the rate of proenkephalin synthesis approximately 10-fold when examined between 16 and 32 h after the drug or hormone addition. Inclusion of nifedipine (1 microM) partially blocked the stimulatory effect of nicotine, but not that of vasoactive intestinal peptide or histamine, or proenkephalin synthesis. Theophylline, tetrabenazine, and angiotensin II also increased the rate of proenkephalin synthesis (three- to eight-fold). These increases in the apparent rate of proenkephalin synthesis were not attributable to altered [35S]methionine specific radioactivity or rates of turnover and did not reflect similar increases in total protein synthesis. The half-life for turnover of Met-enkephalin sequences was 3-4 days in the cultured chromaffin cell. These studies directly show that proenkephalin synthesis is the primary regulatory step in control of chromaffin cell opioid peptide content.
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PMID:Regulation of proenkephalin synthesis in adrenal medullary chromaffin cells. 199 99

Limited proteolysis was used to probe and compare the conformation of the rat lung vasoactive intestinal peptide (VIP) receptor in membrane-bound and detergent-solubilized states. It had been shown previously that the activity of the detergent-solubilized VIP receptor is sensitive to the nature of the detergent used for extraction (Patthi, S., Simerson S. and Velicelebi, G. (1988) J. Biol. Chem., 263, 19363-19369). Receptors that were extracted from the membrane using digitonin retained the ability to bind 125I-VIP, while those solubilized in Triton X-100 displayed little or no detectable activity. In order to correlate the differences observed in the activity of the receptor with its folded state, membrane-bound and detergent-solubilized receptors were covalently labeled with 125I-VIP and subjected to limited proteolysis using trypsin, chymotrypsin or carboxypeptidase Y. Digitonin-solubilized receptors most closely resembled the membrane-bound protein in terms of protease sensitivity and proteolytic cleavage products. By contrast, receptors solubilized in Triton X-100 displayed increased sensitivity to proteases and produced distinctly different proteolytic patterns. Thus, the differences observed in the activities of receptors solubilized in digitonin and those solubilized in Triton X-100 could be correlated with detectable differences in the conformation of the protein in each respective detergent solution. These results suggest that digitonin provides an environment that is more compatible with the native folded state of the receptor, similar to its conformation in the membrane.
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PMID:Limited proteolysis of the vasoactive intestinal peptide receptor: comparison of its folded structure in the membrane-bound and detergent-solubilized states. 215 28

To examine the role of endogenous proteases in limiting the bronchodilating effects of vasoactive intestinal peptide (VIP) in human airway, we studied precontracted bronchial rings from five nonsmokers undergoing heart-lung transplantation for pulmonary hypertension, either primary or secondary to congenital heart disease. The protease inhibitors aprotinin, leupeptin, phosphoramidon, and soybean trypsin inhibitors significantly potentiated the bronchodilator response to VIP. Even in the presence of the four protease inhibitors, VIP-induced bronchodilation reversed spontaneously in some tissues. These studies show that degradation by endogenous airway proteases is an important determinant of the bronchodilating potency of VIP in isolated human airway.
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PMID:Protease inhibitors potentiate smooth muscle relaxation induced by vasoactive intestinal peptide in isolated human bronchi. 218 92


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