Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

For comparative studies on the esterase activities of thrombin and trypsin N(alpha)-arylsulfonyl-L-arginine methyl esters were synthetised containing in aromatic ring substituents of different polar nature, size and hydrophobicity. The kinetics of their hydrolysis by thrombin and trypsin were measured. Values of Km and kcat in steady-state conditions were determined. It was shown, that thrombin-catalysed hydrolysis was more sensitive than that of trypsin to the nature of substituents of arylsulfonyl group and determined by their polar and steric effects. A line correlation between specificity constants (kcat/Km) and sigma and Es of substituents were demonstrated. The difference in reactivity of compounds under investigation is suggested to depend on alterations of stability of hydrogen bond between arylsulfonylamide nitrogen atom of substrate and the active center of the enzyme due to changes in the acidity of the arylsulfonylamide group affected by substituent of the benzene ring.
 ...
PMID:[Dependence of thrombin- and trypsin-catalyzed hydrolysis of N-alpha-arylsulfonyl-L-arginine methyl esters on the structure of acylamide part of substrates]. 2 Sep 97

The trypsin assailability of food proteins (bread, dried milk and egg powder pastes) subjected for different periods of time to the action of the gastric juice directly in the stomach was studied by taking account of the specific topography of its content. It is shown that foodstuffs proteins can be increasingly assailable with trypsin as a result of the action exerted upon them in the stomach by the secretion of its glands. For different food proteins and at different time after feeding the animals as well as in different layers of the gastric contents this effect manifests itself dissimilarly. The trypsin assailability of food proteins increases in the layer near the mucosa and in the antral layers of the gastric contents. A higher trypsin assailability of food proteins is directly related to the level of the proteins hydrolysis in the stomach, to the acidity of the gastric contents and, especially, to its proteolytic activity.
 ...
PMID:[Increase in tryptic digestibility of dietary proteins in the stomach]. 2 10

Studied was the effect of some physical and chemical factors--heating, acidity, treatment with ultraviolet rays, and enzyme treatment--on the activity of the Brucella abortus 99 cell wall antigen. The activity of the antigen was determined through the microreaction of complement-fixing after Kolmer. It was found that the antigen was most sensitive to acid treatment and treatment with ultraviolet rays, and was more slightly sensitive to the effect of alkaline agents and pronase. Besides, the antigen proved heat-resistant and did not lose its activity after treatment with trypsin and alph- and beta-amylase. The chemical nature of the epitopes (the determinant groups), substantiating the activity of the antigen is briefly discussed.
 ...
PMID:[Effect of physical and chemical factors on the antigenic activity of the cell walls of Brucella abortus 99]. 3 83

A study was made on the in vitro characteristics and in vivo biological activities of a leukotactic factor derived from psoriatic scale (PLF). Sephadex G-75 chromatography showed that PLF eluted in the region of the 12,500 dalton protein marker. It resisted heating, lyophilization, acidity (pH 3) and alkalinity (pH 11), but was destroyed by trypsin digestion. The substance attracted polymorphonuclear leukocytes (PMNs) in vitro; this ability was inhibited by antiserum to C3a and was partially reduced by antiserum to C5. Although PLF showed strong chemotactic activity for PMNs, its activity for mononuclear cells was only mild. Intradermal injection of PLF into man or guinea-pig produced an erythematous response with dense tissue neutrophilia, the time course of which was similar to that of the Arthus response. PLF also provoked increased vascular permeability in guinea-pig skin. Moreover, repeated intradermal injection of PLF to the same site in guinea-pigs led to moderate acanthosis of the overlying epidermis. These observations strongly suggest that transepidermal migration of leukocytes in psoriatic lesions is provoked by PLF, whose activity appears to reflect that of complement cleavage products, particularly C3a, presumably produced by complement activation in the subcorneal region of the epidermis. Furthermore, it is postulated that PLF may be a factor which plays a crucial role in the production of typical psoriasiform tissue changes.
 ...
PMID:Characterization of a leukotactic factor derived from psoriatic scale. 58 64

Nine normal subjects were studied before and after intragastric instillation of a liquid meal. Gastric emptying rates of acid and pancreaticobiliary secretions were quantitated by means of a dilution indicator technique. A significant, positive correlation was found between load of acid to the duodenum and the concentration of secretin in plasma. No correlation was found between load of the bile acids and plasma secretin. The buffering capacity of gastric contents should be taken into account when fasting and postprandial periods are compared. Plasma secretin concentration remained low during the first postprandial hour. Maximum secretin concentrations and duodenal disappearance rate of acid was observed 1 1/2-2 h after instillation of the meal. In contrast, trypsin output was maximum within 10 min. The data support the concept that in man release of secretin is governed principally by the amount of hydrogen ions emptied into duodenum and indicate the importance of secretin in the late postprandial period, when the acidity of the gastric contents is high.
 ...
PMID:Meal-stimulated secretin release in man: effect of acid and bile. 733 39

Acceptability and keeping quality of two soymilk samples produced by hot water grinding and by presoaking in NaHCO3 was determined in Morogoro town. In terms of flavour and taste the two samples were significantly different from cow's milk (p < 0.05) but when vanilla was added (0.5 ml/l) the two samples were not significantly different from cow's milk. As estimated by using pH, titratable acidity and standard Plate Count, the milk samples could be kept at room temperature (25 +/- 2 degrees C) for up to 12 hours. The destroy 99% of the trypsin inhibitors in the soymilk samples, 45 minutes at 98 degrees C were needed for the alkaline presoaked milk while 75 minutes were needed for the plain water presoaked soymilk.
 ...
PMID:Acceptability and keeping quality of soymilk in Tanzania. 785 85

The 1H and 13C NMR of trypsin stabilized by chemical modification with a hydrophilic polymer have been obtained in a wide range of pH (1.0-11.0). The spectral features referred to some nuclei of the "catalytic triad" have been identified using different NMR techniques as well as chemical modification with selective reagents. It was found that the monoprotonation of this system results in a quasi-symmetrical hydrogen bond formed between the basic groups which provided explanation for the discrepancies between the experimental findings obtained by different authors concerning the protonation site in this catalytic system. Simulation of the catalytic triad by a 15N-labelled low molecular model suggests that an increase in the OH-group acidity is unaccompanied by a discrete double proton transfer; however, a smooth shift of the bridging protons from one basic atom to another occurs with quasi-symmetrical hydrogen bonds formed in intermediate cases. On the basis of experimental data a new concept has been proposed for the mechanism of acid-base catalysis performed by pains of weak basic groups, such as His-Im and Asp(Glu)-COO- (pKa = 3-7) which are not capable of proton abstraction from alcoholic or water OH-groups (pKa > 13). The catalysis may consist in changing the charge densities on the reacting groups due to strong H-bonding and, on the other hand, in facilitating the free movement of a proton in the field of several basic atoms when going along the reaction coordinate. The energy of very strong hydrogen bonds thus formed diminishes the activation energy of the reaction.
 ...
PMID:[Study of hydrogen bonds in the "catalytic triad" of trypsin by NMR spectra at 1H, 13C, and 15N nuclei]. 804 88

Oral pancreatic enzyme supplements, including those protected from gastric acidity by enteric coating, often achieve only partial correction of pancreatic steatorrhoea. To characterise the mechanisms involved in vivo, eight patients with steatorrhoea due to advanced pancreatic insufficiency and nine healthy controls were studied. Two sets of studies (small bowel intubation and five day faecal fat quantification) were randomly performed while patients were either on enteric coated pancreatin or equivalent placebo. A 260 cm long multilumen tube was used for double marker perfusion of two 20 cm segments located in the duodenum and in the ileum respectively. Luminal pH, flow, and trypsin and lipase activity outputs were measured at each segment for four hours postcibally. Placebo treated patients with pancreatic steatorrhoea had low enzyme outputs in the duodenal test segment and even lower outputs in the ileal segment. Pancreatin treatment significantly decreased steatorrhoea (p < 0.05) and increased luminal enzyme outputs (p < 0.05). The increase was much greater in the ileal than in the duodenal segment. Thus enteric coated pancreatin treatment abolished the normal gradient between postcibal duodenal and ileal lipase output. The results suggest that enteric coated pancreatin nearly corrects severe pancreatic steatorrhoea. The ingested lipase was utilised inefficiently, however, as luminal enzyme activity in the ileum was enhanced to a greater extent than in the duodenum, and consequently the absorptive potential of the small bowel was only partially utilised.
 ...
PMID:Fate of oral enzymes in pancreatic insufficiency. 850 76

The role of cortisol in the prenatal development of digestive enzymes in the abomasum (prochymosin and pepsinogen) and pancreas (amylase, trypsin, chymotrypsin) has been investigated in the fetal lamb during late gestation. The abomasum and pancreas were collected from 22 unoperated control fetuses (99-145 days gestation; term, 145 +/- 2 days), from seven pairs of twins infused with either saline or cortisol for five days preceding delivery at 127-133 days, and from four 139-143-day-old fetuses adrenalectomized at 120-123 days. Developmental increases (2-8-fold) occurred in protease concentrations in the fetal abomasum and in amylase and chymotrypsin contents in the fetal pancreas. These increases paralleled the normal prepartum rise in fetal plasma cortisol. In addition, the enzyme values were significantly higher in cortisol-infused than in saline-infused fetuses (with the exception of pancreatic amylase) and were significantly lower in adrenalectomized fetuses than in control fetuses at term. The pH of abomasal fluid remained neutral (pH 6.8-8.0) during late gestation and was not affected by cortisol treatment or adrenalectomy. The results suggest that cortisol stimulates the development of the exocrine abomasum and pancreas in fetal sheep and may, thereby, increase the digestive capacity in neonatal lambs. Compared with the pig, another long-gestation species, the sheep has an early development of gastric pepsinogen but a late development of gastric acidity and pancreatic protease activities.
 ...
PMID:Maturational effects of cortisol on the exocrine abomasum and pancreas in fetal sheep. 860 79

Gastric and pancreatic lipases are enzymes that play a pivotal role in the digestion of dietary fat. Orlistat, a semisynthetic derivative of lipstatin, is a potent and selective inhibitor of these enzymes, with little or no activity against amylase, trypsin, chymotrypsin and phospholipases. It exerts its effect within the gastrointestinal (GI) tract. Orlistat acts by binding covalently to the serine residue of the active site of gastric and pancreatic lipases. When administered with fat-containing foods, orlistat partially inhibits hydrolysis of triglycerides, thus reducing the subsequent absorption of monoaclglycerides and free fatty acids. This effect can be measured using 24h faecal fat excretion as a representative pharmacodynamic parameter. Orlistat's pharmacological activity is dose-dependent and can be described by a simple Emax model which exhibits an initial steep portion of the dose-response curve with a subsequent plateau (approximately 35% inhibition of dietary fat absorption) for doses above 400 mg/d. At therapeutic doses (120 mg tid with main meals) administered in conjunction with a well balanced, mildly hypocaloric diet, the inhibition of fat absorption (approximately 30% of ingested fat) contributes to an additional caloric deficit of approximately 200 calories. Orlistat does not produce significant disturbances to GI physiological processes (gastric emptying and acidity, gallbladder motility, bile composition and lithogenicity) or to the systemic balance of minerals and electrolytes. Similarly, orlistat does not affect the absorption and pharmacokinetics of drugs with a narrow therapeutic index (phenytoin, warfarin, digoxin) or compounds frequently used by obese patients (oral contraceptives, glyburide, pravastatin, slow-release nifedipine).
 ...
PMID:Mode of action of orlistat. 922 72


1 2 3 Next >>