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)

Inhibitory nonadrenergic noncholinergic (i-NANC) nerves are the only neural bronchodilator pathway in human airways. Possible candidates for the neurotransmitter include vasoactive intestinal peptide (VIP) and nitric oxide (NO) and purines such as ATP. We have investigated the potential role of these neurotransmitters. Phosphoramidon (10(-5) M) significantly potentiated relaxations to low doses of VIP with no effect on i-NANC responses. Relaxations induced by VIp were abolished with alpha-chymotrypsin (2 U/ml), but i-NANC responses were unaffected. Reactive blue 2 had no effect on i-NANC neural responses, indicating that endogenous ATP was not involved. The NO synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME, 10(-4) M) produced a concentration-dependent inhibition of the i-NANC response, producing almost complete inhibition at every frequency studied (0.5-40 Hz), whereas L-NG-monomethyl arginine was effective only at low stimulation frequencies. The inhibitory effect of L-NAME was partially reversed by L- but not D-arginine, and D-NAME was without effect. These results suggest that in human tracheal segments the neural bronchodilator response is mediated by NO, and there is no functional evidence for implicating VIP in this response.
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PMID:Inhibitory NANC nerves in human tracheal smooth muscle: a quest for the neurotransmitter. 136 24

These studies test the hypothesis that the generation of colonic slow waves can be modulated by stimulation of intrinsic enteric nerves and attempt to identify a neurotransmitter that may be responsible for this change in slow-wave activity. Isolated segments from the mid-colon of the cat generated regular, continuous slow waves at 6.5 +/- 1.1 cpm. Activation of the intrinsic nerves by electrical field stimulation transiently reduced the rate of slow-wave generation to 4.7 +/- 0.7 cpm (P less than 0.001). The response to electrical stimulation was blocked by tetrodotoxin and alpha-chymotrypsin. The following antagonists were not effective in blocking the response: atropine, hexamethonium, phenoxybenzamine, propranolol, methysergide, naloxone, or imidazole. Vasoactive intestinal polypeptide (5 x 10(-7) M) decreased slow wave frequency to 4.5 +/- 0.4 cpm. Vasoactive intestinal polypeptide (VIP) fragment 10-28 inhibited the effect of electrical field stimulation but also decreased the slow-wave frequency. VIP-immunoreactive nerves were much more abundant in the plexus submucosus extremus than in the circular muscle of the muscularis externa. Thus, pacemakers for colonic slow waves may be modulated by intrinsic colonic nerves, and vasoactive intestinal polypeptide may be the neurotransmitter responsible for this modulation.
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PMID:Enteric neural modulation of slow-wave activity in cat colon. 167 68

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

The effect of a milk substitute diet containing concentrated soya protein on secretory functions of the abomasum and pancreas and on plasma concentrations of gut hormones and soya antibodies was studied. Sixteen calves aged 12-19 weeks were given a milk substitute in which a major part of the protein source was either soya concentrate (soya diet) or skim milk (control diet). The soya diet was prepared by hot aqueous ethanol extraction of soya bean meal to remove oligosaccharides and inactivate antigenic constituents. Circulatory IgG antibodies against soya proteins were found in all of the calves when they were 16 weeks of age. Their titres increased slightly between 16 and 19 weeks, irrespective of the diet. It seems unlikely that the presence of these antibodies was related specifically to the feeding of the soya concentrate. At slaughter the weight of the gastric mucosa and pancreas and quantities of pancreatic protein together with specific activities of trypsin and chymotrypsin were significantly lower (17, 20, 16, 30 and 36%, respectively) with the soya diet. The quantities of enzymes in the gastric mucosa or the specific activity of pancreatic amylase were not affected, whereas that of lipase increased by 26%. Total enzyme activities as well as units per kg live weight gave significant differences only for trypsin and chymotrypsin which were reduced by 43 and 38%, respectively. With the soya diet, fasting concentrations of gastric inhibitory peptide (GIP) and secretin in plasma samples were significantly lower (49 and 34%, respectively). Values of GIP were also lower (54%) 1 h after feeding. In contrast, postprandial values of cholecystokinin (CCK) were 1.4 times greater. No significant differences were found between the two diets for gastrin, vasoactive intestinal peptide (VIP), bovine pancreatic polypeptide (BPP), somatostatine and motilin. In general these observations could be explained, in part, by the more rapid passage of protein and fat from the abomasum to the duodenum following feeds containing soya concentrate. However, these differences in concentrations of gut hormones did not seem to be related to variations in the weights of gastric mucosa and pancreas or activities of pancreatic enzymes.
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PMID:Effect of soya protein on digestive enzymes, gut hormone and anti-soya antibody plasma levels in the preruminant calf. 242 2

1. The effects of peptidase enzymes on non-adrenergic, non-cholinergic (NANC) inhibitory responses of guinea-pig trachea to electrical field stimulation (EFS), and on relaxations induced by vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) have been examined. 2. alpha-Chymotrypsin reduced both the magnitude and, particularly, the duration of the inhibitory response to EFS, whereas papain reduced only the magnitude. Aprotinin, a peptidase inhibitor prevented the effects of alpha-chymotrypsin but was without effect on papain. 3. alpha-Chymotrypsin and papain both abolished relaxant responses to exogenous VIP and PHI. The action of alpha-chymotrypsin was prevented by aprotinin, whereas that of papain was not affected. 4. The peptidases were without effect on concentration-response curves to methacholine or to isoprenaline. It was also observed that, in the absence of the peptidases, aprotinin had no effect on inhibitory responses either to EFS or to exogenous VIP and PHI. 5. It is suggested that neuropeptides, possibly VIP and PHI, released during EFS of guinea-pig trachea, partly mediate NANC relaxations, and that their action may be inhibited by peptidases. However, the lack of effect of aprotinin alone, on responses to EFS, suggests that, if endogenous peptidases are important in terminating the action of neuropeptides, they are resistant to the effect of this particular peptidase inhibitor. It is further suggested that neurogenic relaxation of guinea-pig trachea is also partly mediated by a substance, possibly non-peptide, other than VIP or PHI.
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PMID:Effects of peptidases on non-adrenergic, non-cholinergic inhibitory responses of tracheal smooth muscle: a comparison with effects on VIP- and PHI-induced relaxation. 265 4

Vasoactive intestinal polypeptide (VIP) antiserum, alpha-chymotrypsin, and repeated exposure to VIP markedly reduced relaxations of the mouse anococcygeus muscle to VIP but not to field stimulation. This evidence suggests that VIP does not mediate non-adrenergic, non-cholinergic relaxations in the mouse anococcygeus.
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PMID:Evidence against VIP-involvement in neurogenic relaxations of the mouse anococcygeus muscle. 287

The aim of this study was to determine the effect of wheat bran consumption on exocrine pancreas secretion in pigs. Sixteen Large-White pigs were divided into two groups. The first group (control) was fed a diet without wheat bran and the second one (experimental) a diet containing 40% wheat bran. After one week the animals were fitted with two permanent fistulae (in the pancreatic duct and the duodenum) and/or with a catheter in a carotid artery. After an 8-day recovery period, pancreatic secretion (volume, protein content and output, chymotrypsin, trypsin, lipase and amylase activities) and plasma levels of some gastro-intestinal peptides [secretin, cholecystokinin (CCK), vasoactive intestinal peptide (VIP), somatostatin and pancreatic polypeptide (PP)] were measured over an experimental period of 5 days. The results show that wheat bran intake induced an increase in the volume (+ 115%) and protein output (+ 36%) of the pancreatic juice secreted in a 24-hour period, whereas protein concentration decreased. All enzyme activities were enhanced by wheat bran. The plasma levels of secretin, VIP, somatostatin and PP were higher in the experimental than in the control group. On the contrary, plasma CCK levels were not affected by wheat bran consumption.
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PMID:Effects of wheat bran on exocrine pancreas secretion in the pig. 289 Nov 62

The receptor for vasoactive intestinal peptide (VIP) was identified in rat liver plasma membranes after covalent cross-linking to 125I-VIP by three different agents [disuccinimido dithiobis(propionate), disuccinimido suberate, and succinimido 4-azidobenzoate] and examined by sodium dodecyl sulfate-acrylamide electrophoresis. Regardless of the presence of reducing conditions, two molecular species of the putative VIP binding unit were identified as broad autoradiographic bands of 80,000 and 56,000 daltons (Da). Both the large and small species showed the same high affinity for 125I-VIP binding and subsequent cross-linking (half-maximal inhibition at 3 nM unlabeled VIP). The 80-kDa species was partially converted to the 56-kDa form by denaturing conditions and was extensively degraded when incubated at 20 degrees C for 30 min with 1 microgram/mL chymotrypsin, trypsin, or elastase to fragments that that migrated similarly to the 56-kDa unit. In contrast, the 56-kDa moiety was resistant to attack by serine proteases. Both the 80- and 56-kDa species were microheterogeneous due at least in part to the presence of carbohydrate chains, each species binding fractionally to wheat germ agglutinin (WGA)-agarose (approximately 50%). The WGA-bound fraction (eluted with N-acetylglucosamine) was relatively retarded on acrylamide gels as compared to the WGA-unbound fraction. Exposure of the 80- and 56-kDa species to endo-beta-acetylglucosaminidase F reduced the apparent molecular mass of each by 19 kDa, indicating the presence of complex N-linked carbohydrate chains. The receptor species do not appear to have high-mannose N-linked chains since they did not interact with concanavalin A and were not cleaved by endo-beta-acetylglucosaminidase H.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Vasoactive intestinal peptide receptor on liver plasma membranes: characterization as a glycoprotein. 300 58

Incubation of monolayers of HT29-D4 cells (a clone of the human colonic adenocarcinoma cell line HT29) in the presence of 17.5 microM cycloheximide resulted in an increase in the number of vasoactive intestinal peptide (VIP) binding sites at the cell surface without any change in the affinity of receptor for its ligand. The increase in 125I-VIP-binding capacity was dose-dependent between 0.35 microM and 17.5 microM cycloheximide and was correlated with the inhibition of protein biosynthesis. At higher concentrations of drug (17.5-100 microM) a plateau corresponding to a twofold increase in VIP-binding capacity was reached independently of the extent of protein synthesis inhibition. We found that VIP receptors of HT29-D4 cells with such an enhanced binding capacity behaved like those of control cells with respect to receptor internalization and recycling (i.e. the cycle of occupied receptors was insensitive to cycloheximide). After inactivation of 90% of cell-surface VIP receptors by alpha-chymotrypsin, we observed a biphasic kinetic of reappearance of VIP-binding sites. 40% of VIP-binding sites reappeared very quickly (less than 5 min) and 100% within 17 h. The fast recovery of VIP receptors was probably due to the deployment of new binding sites from an intracellular pool. The rate and extent of recovery of these receptors were similar in control cells and in cycloheximide-treated cells. However, the slow recovery was inhibited in cycloheximide-treated cells probably because a pool of immature receptors was depleted by the drug before the alpha-chymotrypsin treatment. Our data are consistent with the existence of two different intracellular pathways of occupied and unoccupied VIP receptors.
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PMID:Cycloheximide induces accumulation of vasoactive intestinal peptide (VIP) binding sites at the cell surface of a human colonic adenocarcinoma cell line (HT29-D4). Evidence for the presence of an intracellular pool of VIP receptors. 304 Apr 9

1. Relaxation responses were produced by vagal and field stimulation, respectively, of the whole oesophagus preparation from the rat and of the isolated tunica muscularis mucosae (t.m.m.) preparation from the rat. These relaxation responses persisted in the presence of antagonists of histamine, serotonin, noradrenaline and acetylcholine. 2. Unlike vagally evoked relaxation, that evoked by low-frequency field stimulation, i.e. field-stimulated relaxation (f.s.r.) was generally resistant to tetrodotoxin (TTX). 3. Both types of relaxations exhibited remarkable temperature sensitivity and were abolished by lowering the bath temperature from 37 to 28 degrees C. 4. TTX-resistant relaxations were also produced by scorpion (Leiurus quinquestriatus) venom, the calcium ionophore, A23187 (calimycin) and by increasing the extracellular potassium by 2 mM. The failure of these agents to inhibit f.s.r. is inconsistent with a releasing and/or depleting action on any endogenous mediator. 5. Relaxations produced by vasoactive intestinal peptide (VIP) could be blocked by alpha-chymotrypsin which, however, failed to abolish f.s.r., suggesting that VIP is not the mediator of f.s.r. 6. F.s.r. was completely blocked by the calcium channel antagonists, verapamil (10(-6) M), nifedipine (10(-7) M), and by magnesium (20 mM). 7. Our results indicate that TTX-insensitive relaxations in the isolated t.m.m. are dependent upon extracellular calcium, are due to activation of potential-operated calcium channels and are not mediated by VIP.
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PMID:Tetrodotoxin-sensitive and -insensitive relaxations in the rat oesophageal tunica muscularis mucosae. 311 74


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