scholarly journals Evidence for presence of peptide α-amidating activity in pancreatic islets from newborn rats

1990 ◽  
Vol 267 (1) ◽  
pp. 253-256 ◽  
Author(s):  
A Zhou ◽  
N A Thorn
Keyword(s):  
Ascorbic Acid ◽  
Pancreatic Islets ◽  
Specific Activity ◽  
Soluble Fraction ◽  
Pancreatic Tissue ◽  
Reduced Form ◽  
Newborn Rats ◽  
Ph Optimum ◽  
Old Rats ◽  
Low Levels

The peptide alpha-amidating activity of a homogenate of pancreatic islets from 5-7-day-old rats was investigated, using as substrate a glycine-extended tripeptide (D-Tyr-Val-Gly). The islet homogenates had a marked amidating activity, with a Km of 57 microM, a Vmax. of 185 pmol/h per mg and a pH optimum of 7.0. This activity was dependent on the presence of ascorbic acid (in the reduced form) and Cu2+, the optimum concentrations being 4 mM and 40 microM respectively. On fractionation of the homogenate, the highest specific activity was found in the soluble fraction. Exocrine pancreatic tissue showed very low levels of amidating activity.

Poly(β-L-malate) hydrolase from Plasmodia of Physarum polycephalum

1995 ◽  
Vol 41 (13) ◽  
pp. 192-199 ◽  
Author(s):  
Christian Korherr ◽  
Michael Roth ◽  
Eggehard Holler
Keyword(s):  
Hydrophobic Interaction ◽  
Malic Acid ◽  
Physarum Polycephalum ◽  
Culture Medium ◽  
Specific Activity ◽  
Hydrophobic Interaction Chromatography ◽  
Reduced Form ◽  
Serine Esterase ◽  
Hydroxybutyric Acid ◽  
Ph Optimum

A 68-kDa extracellular glycoprotein from Physarum polycephalum that hydrolyses specifically poly(β-L-malic acid) by removing monomers of L-malic acid in an exolytic manner has been purified and characterized. The enzyme was purified 1740-fold from the culture medium by ammonium sulfate precipitation, hydrophobic interaction chromatography on butyl-Toyopearl, and gel permeation chromatography on Superdex 200 to a specific activity of 9.0 μmol∙min−1∙mg−1. The hydrolase was also purified from the cytosol, which contained 1 mg in 43 g cells in contrast to 1 mg extracellular enzyme in 28 L of culture medium. The pH optimum was pH 3.5 as a result of the effect of an acidic side chain on Vmax and the preferred binding of poly(β-L-malate) in the ionized form. Intracellular hydrolase was only marginally active on [14C]poly(β-L-malate) that had been injected into plasmodia. Poly(L-aspartate), poly(L-glutamate), poly(vinyl sulfate), and poly(acrylate) were neither bound nor degraded by the hydrolase. Poly(β-hydroxybutyric acid), which was considered the reduced form of poly(β-L-malate), was not a substrate. The enzyme is neither a metallo- nor a serine-esterase, and is distinct from poly(3-hydroxybutyric acid) depolymerases. It is related to a glucosidase with respect to hydrophobic interaction chromatography, the pH-activity dependence, and its inhibition with mercuribenzoate, N-bromosuccinimide, and D-gluconolactone, but not the use of the substrates.Key words: poly(β-L-malate), polymalatase, Physarum polycephalum, biodegradative polymer.

scholarly journals The development of arylsulphatase in the small intestine of the rat

1969 ◽  
Vol 114 (2) ◽  
pp. 343-350 ◽  
Author(s):  
S. H. Danovitch ◽  
L. Laster
Keyword(s):  
Small Intestine ◽  
Specific Activity ◽  
Sprague Dawley ◽  
Adult Rats ◽  
Ph Optimum ◽  
Distal Small Intestine ◽  
Sprague Dawley Rats ◽  
Proximal Small Intestine ◽  
Liver And Kidney ◽  
Old Rats

1. Arylsulphatase activity was measured in stomach, proximal and distal third of small intestine, colon, liver and kidney of foetal and neonatal Sprague–Dawley rats and Swiss mice, with nitrocatechol sulphate as substrate. 2. The specific activity in the distal small intestine, but not in the stomach, proximal small intestine or colon, increased about fourfold between 5 and 16 days after birth in both conventional and germ-free rats. 3. No comparable increase occurred in the distal small intestine of the mouse. 4. The specific activity of acid phosphatase in the distal small intestine of the rat rose only slightly when the arylsulphatase activity increased. 5. The pH optimum and Michaelis constant of arylsulphatase activity of the distal small intestine were similar for 1-day-old, 9-day-old and adult rats. 6. When extracts of distal small intestine of 1-day-old and 9-day-old rats were incubated together, the arylsulphatase activities were additive.

scholarly journals Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats

1991 ◽  
Vol 274 (3) ◽  
pp. 739-744 ◽  
Author(s):  
A Zhou ◽  
J H Nielsen ◽  
O Farver ◽  
N A Thorn
Keyword(s):  
Ascorbic Acid ◽  
Pancreatic Islet ◽  
Islet Cells ◽  
Secretory Granules ◽  
Dehydroascorbic Acid ◽  
Pancreatic Tissue ◽  
Biologically Active ◽  
Pancreatic Islet Cells ◽  
High Concentration ◽  
Old Rats

Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.

VARIATION IN GLUTATHIONE AND ASCORBIC ACID CONTENT AMONG SELECTED CULTIVARS OF Phaseolus vulgaris PRIOR TO AND AFTER EXPOSURE TO OZONE

1983 ◽  
Vol 63 (3) ◽  
pp. 733-737 ◽  
Author(s):  
ASAF GURI
Keyword(s):  
Ascorbic Acid ◽  
Phaseolus Vulgaris ◽  
Glutathione Reductase ◽  
Acid Content ◽  
Specific Activity ◽  
Reduced Glutathione ◽  
Ascorbic Acid Content ◽  
Ozone Exposure ◽  
Reduced Form ◽  
Oxidized Glutathione

Measurements of reduced glutathione (GSH) and ascorbic acid (AA) concentrations in the primary leaves of four bean cultivars, two ozone-sensitive (S) and two ozone-insensitive (I), have revealed that GSH concentrations were not significantly different in all four cultivars prior to the exposure to ozone (0.28–0.32 ppm for 8 h); however, after ozone exposure GSH concentrations were significantly lower in the two sensitive cultivars, PHR and 0669, while in the two insensitive tolerants, FH and Nep-2, the drop in GSH concentrations was slight. The assay of glutathione reductase (GR), the enzyme which catalyzed the reduction of oxidized glutathione (GSSG) to its reduced form, namely GSH, indicated that its specific activity in the two insensitive cultivars was almost twice as high as in the two sensitive cultivars. The drop in AA concentration after 8 h of fumigation was moderate (although significant) in all four cultivars, whereas the concentrations of AA in all four cultivars prior to ozone fumigation were not significantly different. From the data it is suggested that differences in GR-specific activity, probably due to different isozymes, could be the reason for insensitivity or sensitivity to ozone among bean cultivars.Key words: Ozone, Phaseolus, glutathione, ascorbic acid, glutathione reductase

scholarly journals Phosphodiesterase II in epithelial cells from guinea-pig and rat small intestine

1974 ◽  
Vol 142 (3) ◽  
pp. 545-553 ◽  
Author(s):  
Peter R. Flanagan ◽  
S. H. Zbarsky
Keyword(s):  
Epithelial Cells ◽  
Guinea Pig ◽  
Specific Activity ◽  
Soluble Fraction ◽  
Gel Filtration ◽  
Equilibrium Density ◽  
Small Intestinal Mucosa ◽  
Ph Optimum ◽  
Triton Wr 1339 ◽  
Small Intestinal

Phosphodiesterase II activity was determined by using a synthetic substrate, the 2,4-dinitrophenyl ester of thymidine 3′-phosphate. The enzyme activity was determined in fractions obtained by differential centrifugation of homogenates of epithelial cells from the small intestinal mucosa of guinea pigs and rats. In guinea-pig preparations phosphodiesterase II occurred with highest specific activity in those fractions rich in succinate dehydrogenase and acid phosphatase. A lysosomal location for the guinea-pig enzyme was indicated by its structure-linked latency and by its association with particles that under-went a characteristic decrease in equilibrium density when Triton WR-1339 was injected into the animals. With rat preparations a much greater proportion of the phosphodiesterase II activity was found in the soluble fraction after ultracentrifugation. The rat enzyme exhibited a lower degree of latency and administration of Triton WR-1339 had no effect. The rat enzyme further differed from that of the guinea pig in other respects; it was more labile at 60°C, it exhibited a lower pH optimum and it had a higher molecular weight as determined by gel-filtration chromatography.

scholarly journals Thermostable glucose isomerase from psychrotolerant Streptomyces species

1970 ◽  
Vol 1 ◽  
pp. 6-10 ◽  
Author(s):  
Bidur Dhungel ◽  
Manoj Subedi ◽  
Kiran Babu Tiwari ◽  
Upendra Thapa Shrestha ◽  
Subarna Pokhrel ◽  
...  
Keyword(s):  
Specific Activity ◽  
Fold Increase ◽  
Glucose Isomerase ◽  
Enzyme Concentration ◽  
Maximal Velocity ◽  
Ph Optimum ◽  
Streptomyces Spp ◽  
Optimum Ph ◽  
Optimum Reaction ◽  
Sepharose 4B

Glucose isomerase (EC 5.3.1.5) was extracted from Streptomyces spp., isolated from Mt. Everest soil sample, and purified by ammonium sulfate fractionation and Sepharose-4B chromatography. A 7.1 fold increase in specific activity of the purified enzyme over crude was observed. Using glucose as substrate, the Michaelis constant (KM<) and maximal velocity (Vmax) were found to be 0.45M and 0.18U/mg. respectively. The optimum substrate (glucose) concentration, optimum enzyme concentration, optimum pH, optimum temperature, and optimum reaction time were 0.6M, 62.14μg/100μl, 6.9, 70ºC, and 30 minutes, respectively. Optimum concentrations of Mg2+ and Co2+ were 5mM and 0.5mM, respectively. The enzyme was thermostable with half-life 30 minutes at 100ºC.DOI: 10.3126/ijls.v1i0.2300 Int J Life Sci 1 : 6-10

THE ROLE OF THE MOTHER IN 131I METABOLISM OF SUCKING AND WEANLING RATS

1965 ◽  
Vol 43 (3) ◽  
pp. 431-436 ◽  
Author(s):  
M. Samel ◽  
A. Caputa
Keyword(s):  
Urinary Bladder ◽  
In Utero ◽  
The State ◽  
Newborn Rats ◽  
Weanling Rats ◽  
Immature Rats ◽  
Other Substances ◽  
Old Rats

In newborn rats the mother provokes the emptying of the urinary bladder by stimulating the perineum with her tongue. The possibility that mothers may thereby ingest the urine of their young has been studied by means of 131I on nine litters of rats aged 10 to 29 days. The results indicate that a considerable quantity of 131I administered intraperitoneally to 10- and 18-day-old rats, which were then reunited with their mothers for 4 hours, reappears in the organism of uninjected nurslings after passing through the organism of the mother. The amount of 131I transferred from injected rats into the bodies of isolated uninjected rats of the same litter decreased during the period of weaning. The observed recirculation of 131I between immature rats and their mothers in both directions may represent a saving mechanism which might include several other substances and would compensate for their loss via the milk, and suggests a new aspect of maternal–neonatal interrelationship which appears as a continuation of the state existing in utero.

Expression of a novel FGF in the Xenopus embryo. A new candidate inducing factor for mesoderm formation and anteroposterior specification

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 711-720 ◽  
Author(s):  
H.V. Isaacs ◽  
D. Tannahill ◽  
J.M. Slack
Keyword(s):  
Specific Activity ◽  
Biological Properties ◽  
The Body ◽  
Mesoderm Induction ◽  
Gastrula Stage ◽  
Blastula Stage ◽  
Mesoderm Formation ◽  
Low Levels

We have cloned and sequenced a new member of the fibroblast growth factor family from Xenopus laevis embryo cDNA. It is most closely related to both mammalian kFGF (FGF-4) and FGF-6 but as it is not clear whether it is a true homologue of either of these genes we provisionally refer to it as XeFGF (Xenopus embryonic FGF). Two sequences were obtained, differing by 11% in derived amino acid sequence, which probably represent pseudotetraploid variants. Both the sequence and the behaviour of in vitro translated protein indicates that, unlike bFGF (FGF-2), XeFGF is a secreted molecule. Recombinant XeFGF protein has mesoderm-inducing activity with a specific activity similar to bFGF. XeFGF mRNA is expressed maternally and zygotically with a peak during the gastrula stage. Both probe protection and in situ hybridization showed that the zygotic expression is concentrated in the posterior of the body axis and later in the tailbud. Later domains of expression were found near the midbrain/hindbrain boundary and at low levels in the myotomes. Because of its biological properties and expression pattern, XeFGF is a good candidate for an inducing factor with possible roles both in mesoderm induction at the blastula stage and in the formation of the anteroposterior axis at the gastrula stage.

Ontogeny of pepsin secretory response to secretagogues in isolated rat gastric glands

1986 ◽  
Vol 250 (2) ◽  
pp. G200-G204 ◽  
Author(s):  
J. Yahav ◽  
P. C. Lee ◽  
E. Lebenthal
Keyword(s):  
Term Neonate ◽  
Ionophore A23187 ◽  
Newborn Rats ◽  
Dibutyryl Camp ◽  
Gastric Glands ◽  
Cholecystokinin Octapeptide ◽  
Rat Pups ◽  
Isolated Gastric Glands ◽  
Old Rats ◽  
Isolated Rat

By use of isolated gastric glands from rats at various ages, we demonstrated that full-term neonate and 1-day-old rats showed no response to cholecystokinin octapeptide (CCK-OP), carbachol, or Ca2+ ionophore. The same glands, however, were responsive to dibutyryl cAMP. A mature response was not found until the pups were 2 days old. Injection of hydrocortisone into newborn rats led to an increase in pepsinogen concentrations in gastric glands and also an increased responsiveness to CCK-OP, carbachol, and Ca2+ ionophore A23187 24 h after administration. Hydrocortisone thus caused precocious maturation of both pepsinogen accumulation and pepsinogen secretory responsiveness of gastric glands in rat pups.

scholarly journals Inhibition of Endocannabinoid-Metabolizing Enzymes in Peripheral Tissues Following Developmental Chlorpyrifos Exposure in Rats

2017 ◽  
Vol 36 (5) ◽  
pp. 395-402 ◽  
Author(s):  
Robert W. Buntyn ◽  
Navatha Alugubelly ◽  
Rachel L. Hybart ◽  
Afzaal N. Mohammed ◽  
Carole A. Nail ◽  
...  
Keyword(s):  
Immune Function ◽  
Specific Activity ◽  
Fatty Acid Amide Hydrolase ◽  
Acid Amide ◽  
Metabolizing Enzymes ◽  
Peripheral Tissues ◽  
Rat Pups ◽  
Physiological Processes ◽  
Low Levels ◽  
Amide Hydrolase

Repeated developmental exposure to the organophosphate (OP) insecticide chlorpyrifos (CPF) inhibits brain fatty acid amide hydrolase (FAAH) activity at low levels, whereas at higher levels, it inhibits brain monoacylglycerol lipase (MAGL) activity. FAAH and MAGL hydrolyze the endocannabinoids anandamide (AEA) and 2-arachidonylglycerol (2-AG), respectively. Peripherally, AEA and 2-AG have physiological roles in the regulation of lipid metabolism and immune function, and altering the normal levels of these lipid mediators can negatively affect these processes. Exposure to CPF alters brain endocannabinoid hydrolysis activity, but it is unclear whether low-level exposure alters this activity in peripheral tissues important in metabolic and immune function. Therefore, rat pups were exposed orally from day 10 to 16 to 0.5, 0.75, or 1.0 mg/kg CPF or 0.02 mg/kg PF-04457845 (a specific FAAH inhibitor). At 12 hours postexposure, FAAH, MAGL, and cholinesterase (ChE) activities were determined. All treatments inhibited FAAH activity in brain, spleen, and liver. CPF inhibited ChE activity in spleen and liver (all dosages) and in brain (highest dosage only). CPF inhibited total 2-AG hydrolysis and MAGL-specific activity in brain and spleen (high dosage only). In liver, total 2-AG hydrolysis was inhibited by all treatments and could be attributed to inhibition of non–MAGL-mediated 2-AG hydrolysis, indicating involvement of other enzymes. MAGL-specific activity in liver was inhibited only by the high CPF dosage, whereas PF-04457845 slightly increased this activity. Overall, exposure to low levels of CPF and to PF-04457845 can alter endocannabinoid metabolism in peripheral tissues, thus potentially affecting physiological processes.

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