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Journal of Comparative Physiology. B,... Jul 2013Digestive enzymes produced by the pancreas and intestinal epithelium cooperate closely during food hydrolysis. Therefore, activities of pancreatic and intestinal enzymes...
Digestive enzymes produced by the pancreas and intestinal epithelium cooperate closely during food hydrolysis. Therefore, activities of pancreatic and intestinal enzymes processing the same substrate can be hypothesized to change together in unison, as well as to be adjusted to the concentration of their substrate in the diet. However, our knowledge of ontogenetic and diet-related changes in the digestive enzymes of birds is limited mainly to intestinal enzymes; it is largely unknown whether they are accompanied by changes in activities of enzymes produced by the pancreas. Here, we analyzed age- and diet-related changes in activities of pancreatic enzymes in five passerine and galloanserine species, and compared them with simultaneous changes in activities of intestinal enzymes. Mass-specific activity of pancreatic amylase increased with age in young house sparrows but not in zebra finches, in agreement with changes in typical dietary starch content and activity of intestinal maltase. However, we found little evidence for the presence of adaptive, diet-related modulation of pancreatic enzymes in both passerine and galloanserine species, even though in several cases the same birds adaptively modulated activities of their intestinal enzymes. In general, diet-related changes in mass-specific activities of pancreatic and intestinal enzymes were not correlated. We conclude that activity of pancreatic enzymes in birds is under strong genetic control, which enables evolutionary adjustment to typical diet composition but is less adept for short term, diet-related flexibility.
Topics: Aging; Amylases; Animals; Birds; Chymotrypsin; Diet; Pancreas; Trypsin
PubMed: 23269614
DOI: 10.1007/s00360-012-0731-2 -
The Journal of Physiology Jun 19741. Enzyme secretion in response to short duration vagal stimulation or to rapid I.V. injections of cholecystokinin-pancreozymin (CCK-PZ) or gastrin or to intra-arterial...
1. Enzyme secretion in response to short duration vagal stimulation or to rapid I.V. injections of cholecystokinin-pancreozymin (CCK-PZ) or gastrin or to intra-arterial injections of acetylcholine is a function of the volume of juice secreted and not primarily a function of time.2. The output of amylase in response to each stimulus occurred in a constant volume of approximately 15 drops (0.5 ml.) regardless of the rate of background secretin stimulated flow of water and electrolyte.3. It is argued that because amylase secretion occurs in this constant volume, it is due to the rapid secretion of enzyme into the duct system from the acini, and subsequently the secretin stimulated secretion of water and bicarbonate washes the enzyme from the duct system.4. When enzyme secretion is stimulated an increase in the electrical conductance (measured at 1.592 kHz) occurs across the tail of the pancreas. This increased conductance has two components. An early peak associated with the extrusion of enzyme from the acinar cell and a later peak which is probably due to vasodilatation.5. Atropine was without effect on both enzyme secretion and the conductance record when the stimulant was CCK-PZ. Atropine blocked enzyme secretion and both peaks of the conductance record in response to stimulation by acetylcholine. Atropine blocked enzyme secretion and abolished the early phase of the conductance record, on vagal stimulation. It was without effect on the later peak which probably indicates an atropine resistant vasodilation of the pancreatic vessels.6. When the vagus is stimulated on a background of submaximal electrolyte secretion caused by the intravenous infusion of secretin, the volume rate of secretion and the rate of amylase secretion follow a similar time course. The maximal volume response occurred between 7 Hz and 15 Hz and the maximal amylase output per impulse was at 5 Hz.
Topics: Acetylcholine; Amylases; Animals; Atropine; Cats; Cholecystokinin; Electric Conductivity; Electric Stimulation; Gastrins; Kinetics; Pancreas; Pancreatic Juice; Time Factors; Vagus Nerve
PubMed: 4854925
DOI: 10.1113/jphysiol.1974.sp010577 -
Journal of Molecular Biology Jun 2007Bile salt interactions with phospholipid monolayers of fat emulsions are known to regulate the actions of gastrointestinal lipolytic enzymes in order to control the...
Bile salt interactions with phospholipid monolayers of fat emulsions are known to regulate the actions of gastrointestinal lipolytic enzymes in order to control the uptake of dietary fat. Specifically, on the lipid/aqueous interface of fat emulsions, the anionic portions of amphipathic bile salts have been thought to interact with and activate the enzyme group-IB phospholipase A2 (PLA2) derived from the pancreas. To explore this regulatory process, we have determined the crystal structures of the complexes of pancreatic PLA2 with the naturally occurring bile salts: cholate, glycocholate, taurocholate, glycochenodeoxycholate, and taurochenodeoxycholate. The five PLA2-bile salt complexes each result in a partly occluded active site, and the resulting ligand binding displays specific hydrogen bonding interactions and extensive hydrophobic packing. The amphipathic bile salts are bound to PLA2 with their polar hydroxyl and sulfate/carboxy groups oriented away from the enzyme's hydrophobic core. The impaired catalytic and interface binding functions implied by these structures provide a basis for the previous numerous observations of a biphasic dependence of the rate of PLA2 catalyzed hydrolysis of zwitterionic glycerophospholipids in the presence of bile salts. The rising or activation phase is consistent with enhanced binding and activation of the bound PLA2 by the bile salt induced anionic charge in a zwitterionic interface. The falling or inhibitory phase can be explained by the formation of a catalytically inert stoichiometric complex between PLA2 and any bile salts in which it forms a stable complex. The model provides new insight into the regulatory role that specific PLA2-bile salt interactions are likely to play in fat metabolism.
Topics: Animals; Bile Acids and Salts; Binding Sites; Crystallography, X-Ray; Enzyme Activation; Humans; Molecular Sequence Data; Molecular Structure; Pancreas; Phospholipases A; Phospholipases A2; Protein Structure, Tertiary; Swine
PubMed: 17434532
DOI: 10.1016/j.jmb.2007.03.034 -
The Journal of Cell Biology Apr 1971The subcellular components involved in the synthesis, transport, and discharge of secretory proteins in the guinea pig pancreatic exocrine cell have been isolated from...
The subcellular components involved in the synthesis, transport, and discharge of secretory proteins in the guinea pig pancreatic exocrine cell have been isolated from gland homogenates by differential and gradient centrifugation. They include rough and smooth microsomes derived respectively from the rough endoplasmic reticulum and Golgi periphery, a zymogen granule fraction consisting mainly of mature zymogen granules and a smaller population of condensing vacuoles, and a plasmalemmal fraction. Membrane subfractions were obtained from the particulate components by treatment with mild (pH 7.8) alkaline buffers which extract the majority (>95%) of the content of secretory proteins, allowing the membranes to be recovered from the extracting fluid by centrifugation. The purity of the fractions was assessed by electron microscopy and by assaying marker enzymes for cross-contaminants. The rough and smooth microsomes were essentially free of mitochondrial contamination; the smooth microsomes contained <15% rough contaminants. The zymogen granule fraction and its derived membranes were free of rough microsomes and contained <3% contaminant mitochondria. The plasmalemmal fraction was heterogeneous as to origin (deriving from basal, lateral, and apical poles of the cell) and contained varying amounts of adherent fibrillar material arising from the basement membrane and terminal web. The lipid and enzymatic composition of the membrane fractions are described in the following reports.
Topics: Amylases; Animals; Buffers; Cell Membrane; Centrifugation, Density Gradient; Chymotrypsin; Cytoplasm; Electron Transport Complex IV; Endoplasmic Reticulum; Enzyme Precursors; Golgi Apparatus; Guinea Pigs; Histocytochemistry; Male; Methods; Microscopy, Electron; Mitochondria; Pancreas; Phospholipids; RNA; Ribonucleases; Succinate Dehydrogenase; Trypsin
PubMed: 4324564
DOI: 10.1083/jcb.49.1.109 -
Journal of Physiology and Pharmacology... Jun 2000Recent studies clearly demonstrate that Helicobacter pylori (H. pylori) infection of the stomach causes persistent elevation of ammonia (NH3) in gastric juice leading to...
BACKGROUND
Recent studies clearly demonstrate that Helicobacter pylori (H. pylori) infection of the stomach causes persistent elevation of ammonia (NH3) in gastric juice leading to hypergastrinemia and enhanced pancreatic enzyme secretion.
METHODS
The aim of this study is to evaluate the influence of NH4OH on plasma gastrin level and exocrine pancreatic secretion in vivo in conscious dogs equipped with chronic pancreatic fistulas and on secretory activity of in vitro isolated acini obtained from the rat pancreas by collagenase digestion. The effects of NH4OH on amylase release from pancreatic acini were compared with those produced by simple alkalization of these acini with NaOH.
RESULTS
NH4OH given intraduodenally (i.d.) in increasing concentrations (0.5, 1.0, 2.0, 4.0, or 8.0 mM/L) resulted in an increase of pancreatic protein output, reaching respectively 9%, 10%, 19%, 16% and 17% of caerulein maximum in these animals and in a marked increase in plasma gastrin level. NH4OH (8 x 0 mM/L, i.d.) given during intravenous (i.v.) infusion of secretin (50 pmol/kg-h) and cholecystokinin (50 pmol/kg-h) reduced the HCO3 and protein outputs by 35% and 37% respectively, as compared to control obtained with infusion of secretin plus cholecystokinin alone. When pancreatic secretion was stimulated by ordinary feeding the same amount of NH4OH administered i.d. decreased the HCO3- and protein responses by 78% and 47% respectively, and had no significant effect on postprandial plasma gastrin. In isolated pancreatic acini, increasing concentrations of NH4OH (10(-7)-10(-4) M) produced a concentration-dependent stimulation of amylase release, reaching about 43% of caerulein-induced maximum. When various concentrations of NH4OH were added to submaximal concentration of caerulein (10(-12) M) or urecholine (10(-5) M), the enzyme secretion was reduced at a dose 10(-5) M of NH4OH by 38% or 40%, respectively. Simple alkalization with NaOH of the incubation medium up to pH 8.5 markedly stimulated basal amylase secretion from isolated pancreatic acini, whereas the secretory response of these acini to pancreatic secretagogues was significantly diminished by about 30%. LDH release into the incubation medium was not significantly changed in all tests indicating that NH4OH did not produce any apparent damage of pancreatic acini and this was confirmed by histological examination of these acini.
CONCLUSIONS
1. NH4OH affects basal and stimulated pancreatic secretion. 2. The excessive release of gastrin may be responsible for the stimulation of basal pancreatic enzyme secretion in conscious animals, and 3. The inhibitory effects of NH4OH on stimulated secretion might be mediated, at least in part, by its direct action on the isolated pancreatic acini possibly due to the alkalization of these acini.
Topics: Alkalies; Ammonia; Ammonium Hydroxide; Amylases; Animals; Bethanechol Compounds; Ceruletide; Dogs; Eating; Enzymes; Gastrins; Hydroxides; In Vitro Techniques; L-Lactate Dehydrogenase; Pancreas; Sodium Hydroxide
PubMed: 10898103
DOI: No ID Found -
European Journal of Biochemistry Jun 1983The N-terminal alpha-helical region of phospholipase A2 is an important part of the enzyme for catalytic activity and lipid binding. Porcine pancreatic phospholipase A2...
Semisynthesis of phospholipase A2. The effect of substitution of amino-acid residues at positions 6 and 7 in bovine and porcine pancreatic phospholipases A2 on catalytic and substrate-binding properties.
The N-terminal alpha-helical region of phospholipase A2 is an important part of the enzyme for catalytic activity and lipid binding. Porcine pancreatic phospholipase A2 has Arg-Ser at positions 6 and 7, whereas the bovine enzyme has Asn-Gly. To pursue further the effects of these variable residues on differences in enzymatic properties, we prepared and studied the following semisynthetic analogs of epsilon-amidinated phospholipase A2 (AMPA): porcine [Ala7]AMPA, [Gly7]AMPA, [Asn6]AMPA, [Asn6-Gly7]AMPA and bovine [Ser7]AMPA and [Arg6-Ser7]AMPA. As we had previously found for the Asn6 leads to Arg bovine substitution, an Asn6-Gly7 leads to Arg5-Ser7 bovine substitution similarly improves the catalytic activity, the affinity for neutral lipid-water interfaces and the capacity to penetrate lecithin monolayers, while just changing Gly7 leads to Ser produces almost no effect on these properties. Ser7 leads to Ala and Ser7 leads to Gly substitutions in porcine AMPA did not affect penetration or lipid binding, although they did diminish catalytic activity (which is true of all substitutions made in the porcine enzyme). Arg6 leads to Asn substitution in porcine AMPA decreases penetration of lecithin monolayers, but not as much as it was improved by the Asn6 leads to Arg substitution in bovine AMPA. In contrast to the dramatic increase in affinity for lipid-water interfaces of Asn6 leads to Arg substitution in bovine AMPA, no decrease in affinity was found for Arg6 leads to Asn substitution in porcine AMPA. This difference is most likely due to the fact that the porcine enzyme has positively charged Lys and His in place of the Lys10, Glu17 pair that lie very close to residue 6 in the bovine structure. It can thus be conclude that (with the exception of Gly7 leads to Ser in bovine AMPA) all the substitutions tried at positions 6 and 7 in bovine and porcine AMPAs have definite effects on the catalytic activity.
Topics: Amides; Amino Acids; Animals; Binding Sites; Catalysis; Cattle; Chemical Phenomena; Chemistry; Lipid Metabolism; Models, Molecular; Pancreas; Phospholipases; Phospholipases A; Phospholipases A2; Species Specificity; Structure-Activity Relationship; Substrate Specificity; Swine
PubMed: 6852036
DOI: 10.1111/j.1432-1033.1983.tb07432.x -
Journal of Dairy Science Mar 1976Bovine pancreatic lipase was isolated in pure form by lyophilization of fresh bovine pancreas, extraction of the enzyme with sucrose solution, fractional precipitation...
Bovine pancreatic lipase was isolated in pure form by lyophilization of fresh bovine pancreas, extraction of the enzyme with sucrose solution, fractional precipitation with ammonium sulfate and acetone, followed by chromatography on Sephadex G-100. The specific activity of the purest lipase fraction was 1750 micromoles fatty acid, liberated in 30 min per milligram of protein, indicating a purification of approximately 473-fold, with an overall yield of about 42%. Homogeneity of the enzyme was confirmed by rechromatography on Sephadex G-100 as well as with the gel electrophoretic and ultracentrifugal techniques. The purified enzyme gave a typical protein ultraviolet absorption spectrum with maximum absorption at 276 nm and minimum at 252 nm. The purified enzyme exhibited a single pH optimum of 8.8 and an isoelectric point near pH 5.5. Its optimum temperature was 37 C, and its optimum substrate concentration was 10%. These properties resembled those of milk lipase.
Topics: Animals; Cattle; Hydrogen-Ion Concentration; Isoelectric Focusing; Lipase; Pancreas; Spectrophotometry, Ultraviolet; Temperature
PubMed: 4478
DOI: 10.3168/jds.S0022-0302(76)84214-2 -
Proceedings of the National Academy of... Feb 1983A pathway from glucose via sorbitol bypasses the control points of hexokinase and phosphofructokinase in glucose metabolism. It also may produce glycerol, linking the...
A pathway from glucose via sorbitol bypasses the control points of hexokinase and phosphofructokinase in glucose metabolism. It also may produce glycerol, linking the bypass to lipid synthesis. Utilization of this bypass is favored by a plentiful supply of glucose--hence, conditions under which glycolysis also is active. The bypass further involves oxidation of NADPH, so the pentose phosphate pathway and the bypass are mutually facilitative. Possible consequences in different organs under normal and pathological, especially diabetic, conditions are detailed. Enzymes with related structures (for example, sorbitol dehydrogenase and alcohol dehydrogenase, and possibly, aldehyde reductase and aldose reductase, respectively) are linked functionally by this scheme. Some enzymes of the bypass also feature in glycolysis (aldolase and alcohol dehydrogenase), and these enzymes, with the reductases involved, are proteins known to occur in different classes or multiple isozyme forms. Two of the enzymes (aldolase and alcohol dehydrogenase) both involve classes with and without a catalytic metal (zinc). The existence of parallel pathways and the occurrence of similar enzymic steps in one pathway may help to explain the abundance and multiplicity of enzymes such as reductases, aldolases, and alcohol dehydrogenases.
Topics: Alcoholism; Aldehyde Reductase; Animals; Brain; Energy Metabolism; Female; Fructose-Bisphosphate Aldolase; Glucose; Humans; Kidney; L-Iditol 2-Dehydrogenase; Lens, Crystalline; Liver; Male; Neurons; Oxidoreductases; Pancreas; Placenta; Pregnancy; Sorbitol
PubMed: 6405381
DOI: 10.1073/pnas.80.4.901 -
Journal of the Chinese Medical... Mar 2010
Topics: Amylases; Humans; Intensive Care Units; Lipase; Pancreas; Pancreatitis
PubMed: 20230996
DOI: 10.1016/S1726-4901(10)70026-5 -
Journal of Lipid Research Jun 1995Monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG) and sulfoquinovosyldiacylglycerols (SQDG) are major lipids in vegetable food. Their digestion...
Monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG) and sulfoquinovosyldiacylglycerols (SQDG) are major lipids in vegetable food. Their digestion and absorption are unknown. This study examines the hydrolysis of galactolipids in vitro with human duodenal contents, pancreatic juice, and purified human pancreatic lipases. Galactolipids were incubated with human duodenal contents, pancreatic juice, pure pancreatic carboxyl ester lipase (CEL), and colipase-dependent lipase with colipase (Lip-Col). Hydrolysis was estimated as release of free fatty acids and by the use of [3H]galactose or [3H]fatty acid-labeled DGDG. Pancreatic juice and duodenal contents hydrolyzed DGDG to fatty acids, digalactosylmonoacylglycerol (DGMG) and water-soluble galactose-containing compounds. The hydrolysis of DGDG was bile salt-dependent and had a pH optimum at 6.5-7.5. Human pancreatic juice released fatty acids from MGDG, DGDG, and SQDG. Purified CEL hydrolyzed all three substrates; the hydrolysis rate was MGDG > SQDG > DGDG. Pure Lip-Col had activity toward MGDG but had little activity against DGDG. Separation of pancreatic juice by Sephadex G100 gel filtration chromatography revealed two peaks with galactolipase activity that coincided with CEL (molecular mass 100 kD) and lipase (molecular mass 50 kD) peaks. In contrast to pure Lip-Col enzymes of the latter peak were as active against DGDG as against MGDG. Thus, DGDG is hydrolyzed both by CEL and by a pancreatic enzyme(s) with a molecular mass of 40-50 kD to fatty acids and lyso DGDG. MGDG, DGDG, and SQDG are all hydrolyzed by human pancreatic juice. Pure CEL hydrolyzed all three substrates.
Topics: Bile Acids and Salts; Carboxylesterase; Carboxylic Ester Hydrolases; Colipases; Dietary Fats; Digestion; Diglycerides; Duodenum; Fatty Acids; Galactolipids; Glycolipids; Humans; Hydrogen-Ion Concentration; Hydrolysis; Lipase; Lipolysis; Pancreas; Pancreatic Juice
PubMed: 7666015
DOI: No ID Found