Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. A neutral peptidase, previously shown to be located in the brush border of the proximal tubule, and assayed by its ability to hydrolyse [(125)I]iodoinsulin B chain was purified from rabbit kidney. 2. The starting material for the purification was a microsomal pellet prepared from a homogenate of cortical tissue. The membrane-bound enzymes were solubilized by treatment with toluene and trypsin. About half the neutral peptidase activity was released by this treatment in a form that no longer sedimented with the microsomal pellet and which penetrated polyacrylamide gels when subjected to disc electrophoresis. Other treatments with detergents or proteolytic enzymes either inactivated the peptidase or failed to convert it into a genuinely soluble form. 3. Chromatography with successive columns of Sephadex G-200, DEAE-cellulose and hydroxyl-apatite yielded an enzyme that was free of other brush-border peptidase activities and which was homogeneous on disc electrophoresis and ultracentrifugation. 4. The purified enzyme attacked [(125)I]iodoglucagon at a rate comparable with that for [(125)I]iodoinsulin B chain. It did not appear to attack proteins (insulin, albumin and casein) that had been similarly iodinated. 5. Unlabelled insulin B chain and unlabelled glucagon were substantially hydrolysed by the endopeptidase, whereas insulin and albumin released only trivial amounts of ninhydrin-reacting material. The resistance of insulin to attack by endopeptidase, even after prolonged incubation, was confirmed by biological and immunoassay. 6. The specificity of the peptidase was determined by analysis of the products after incubating unlabelled insulin B chain, and some oligopeptide substrates, including pentagastrin, with the enzyme. All of the bonds readily cleaved were those involving the alpha-amino group of hydrophobic residues, i.e. x-Leu-, x-Val-, x-Tyr-, x-Phe- and x-Met-, provided that the residues were not C-terminal. 7. The enzyme showed only endopeptidase activity. Substrates suitable for aminopeptidases, carboxypeptidases or esterases were not attacked.
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PMID:The purification and specificity of a neutral endopeptidase from rabbit kidney brush border. 442 92

The effect of 20 L-amino acids upon pancreatic glucagon secretion has been studied in conscious dogs. Each amino acid was administered intravenously over a 15 min period in a dose of 1 mmole/kg of body weight to a group of four or five dogs. Pancreatic glucagon and insulin were measured by radioimmunoassay. 17 of the 20 amino acids caused a substantial increase in plasma glucagon. Asparagine had the most glucagon-stimulating activity (GSA), followed by glycine, phenylalanine, serine, aspartate, cysteine, tryptophan, alanine, glutamate, threonine, glutamine, arginine, ornithine, proline, methionine, lysine, and histidine. Only valine, leucine, and isoleucine failed to stimulate glucagon secretion, and isoleucine may have reduced it. No relationship between glucagon-stimulating activity and insulin-stimulating activity was observed. The amino acids which enter the gluconeogenic pathway as pyruvate and, which are believed to provide most of the amino acid-derived glucose, had a significantly greater GSA than the amino acids which enter as succinyl CoA or as alpha-ketoglutarate. However, pyruvate itself did not stimulate glucagon secretion. The R-chain structure of the amino acid did not appear to be related to its GSA, except that the aliphatic branched chain amino acids, valine, leucine, and isoleucine, were devoid of GSA.
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PMID:Glucagon-stimulating activity of 20 amino acids in dogs. 463 19

Albumin synthesis was measured in the isolated perfused rat liver by using the livers of both well-fed and starved rats. Starvation markedly decreased albumin synthesis. The livers from starved rats were unable to increase synthesis rates after the addition to the perfusates of single amino acids or the addition of both glucagon and tryptophan. Arginine, asparagine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan and valine, added together to ten times their normal peripheral blood concentrations, restored synthesis rates to normal. The plasma aminogram (i.e. the relative concentrations, of amino acids) was altered by depriving rats of protein for 48h. The use of blood from the deprived rats as perfusate, instead of normal blood, decreased albumin synthesis rates significantly by livers obtained from well-fed rats. The addition of single amino acids, including the non-metabolizable amino acid, alpha-aminoisobutyric acid, to the above mixture increased albumin synthesis rates to normal values. It is concluded that amino acids play an important role in the control of albumin synthesis and that more than one mechanism is probably involved.
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PMID:The effects of amino acids on albumin synthesis by the isolated perfused rat liver. 465 17

Dog bone marrow nucleated cells were incubated in media containing labeled L-amino acids, and the cellular accumulation of radioactivity as a function of time was measured and analyzed according to a three-compartment model.(a) The turnover half-time of intracellular histidine arising from extracellular sources was 6.0 +/-0.7 (SEM) min. Similar turnover half-time for serine was 10 +/-2 (SEM) min; for tryptophan, 6.5 +/-1.2 (SEM) min; and for methionine, 4.4 +/-0.6 (SEM) min. Loss of the intracellular amino acids to the extracellular space accounted for the major portion of their turnover.(b) Each of the four amino acids noted above appeared to be actively transported into the cell.(c) At physiologic extracellular histidine concentrations, histidine entered the cell predominantly by a facilitated process with an apparent Michaelis constant of 0.28 mmole/liter and a limiting flux of 14 x 10(-8) mmumole/min per cell. Loss of histidine from the cell appeared to be substantially facilitated with an apparent Michaelis constant greater than that for histidine entry.(d) Insulin and glucagon had no measurable effect on histidine transport across the bone marrow cell membrane.(e) Methionine depressed the influx and the fractional turnover rate of the intracellular pool of both histidine and serine.(f) The extent of cellular accumulation of alpha-N-formiminoglutamate and alpha-N-formylglutamate was about 1/100 that of histidine. alpha-N-formiminoglutamate added to the culture was about (1/4) as effective as histidine in providing monocarbon fragments for DNA thymine synthesis.
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PMID:Kinetics of amino acid transport across bone marrow cell membranes. 544 76

Homogeneous porcine calpain (Ca2+-dependent cysteine proteinase) was found to hydrolyze a variety of peptides and synthetic substrates. Leu-Trp-Met-Arg-Phe-Ala, eledoisin-related peptide, alpha-neoendorphin, angiotensin I, luteinizing hormone-releasing hormone, neurotensin, dynorphin, glucagon, and oxidized insulin B chain were cleaved with a general preference for a Tyr, Met, or Arg residue in the P1 position preceded by a Leu or Val residue in the P2 position. No great difference in specificity was found between low-Ca2+-requiring calpain I and high-Ca2+-requiring calpain II. 4-Methylcoumaryl-7-amide (MCA) derivatives having a Leu(or Val)-Met(or Tyr)-MCA or a Leu-Lys-MCA sequence were also cleaved by either calpain I or calpain II with preference for Leu over Val by a factor of 9 to 16. Calpains I and II showed similar but not identical kinetic behavior for individual substrates. The Km and kcat values ranged from 0.23 to 7.08 mM and 0.062 to 0.805 s-1 for the calpains, while kcat/Km values for the calpains were only 1/433 to 1/5 of those for papain with a given substrate. With succinyl-Leu-Met(or Tyr)-MCA, calpains I and II were half-maximally activated at 12 and 260 microM Ca2+, respectively, and competitively inhibited by leupeptin (Ki = 0.32 microM for I and 0.43 microM for II) or antipain (Ki = 1.41 microM for I and 1.45 microM for II). Thus, this is the first report describing the specificity and kinetics of calpains I and II.
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PMID:Comparative specificity and kinetic studies on porcine calpain I and calpain II with naturally occurring peptides and synthetic fluorogenic substrates. 609 35

A radioassay for nonoxidized methionine in peptides is described; it has advantages over other methods currently used because of its simplicity, sensitivity, accuracy, and applicability to individual peptide components in mixtures and to many samples at a time. Methionyl residues were S-carboxymethylated with iodo[2-14C]acetic acid; iodo[2-3H]acetic acid did not provide a stable radioactive tracer. The labeled peptide was isolated by carboxymethylcellulose chromatography or by isoelectric focusing (IEF) or electrophoresis in polyacrylamide gel, and its radioactivity measured. The assay was applied to corticotropins, alpha-melanotropin, bombesin, glucagon, substance P, parathormone, and calcitonin. Twenty-four to thirty samples were conveniently analyzed at a time with a lower detection limit of less than 1 nmol of methionine per sample. The accuracy of the assay, assessed also by reverse-phase high-performance liquid chromatography, is a consequence of its precision, the specificity of the reaction with iodoacetic acid, and the use of an appropriate standard of the peptide being assayed. Methionine was identified, and could be estimated, in individual peptide components of a mixture by using IEF to separate simultaneously the labeled peptide from iodo[2-14C]acetic acid and from other peptide and protein components. This was facilitated by a convenient method for detecting and quantifying these peptides after IEF. The assay is particularly useful for several peptide hormones whose biological activity depends on their sole methionine residue being in a nonoxidized state. It can be used for monitoring their isolation or synthesis and their stability during processing and storage, as well as for evaluating differences in biological potency between preparations and analogues.
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PMID:A radioassay for nonoxidized methionine in peptides. A method for identifying (after isoelectric focusing) and for estimating biologically active forms of corticotropin and other hormones. 609 26

Methods have been developed for the preparation of suspensions of viable rat pancreatic islet cells and their analysis and sorting in the fluorescence-activated cell sorter (FACS III or IV). Histograms of cell number versus light scattering in a near forward angle (1-15 degrees) demonstrated that viable islet cells produce a broad peak that is distinctly separated from the peaks generated by exocrine cells, erythrocytes, and nonviable cells. Electron microscopic examination and radioimmunoassay of hormone content in fractions collected across the peak showed that glucagon-containing (A) cells scatter less intensely and are concentrated within the left side of the islet cell peak, while somatostatin-containing (D) cells are localized to the far right side, indicating a higher intrinsic light scattering property of the D-cells. The more abundant insulin-containing (B) cells define the center of the islet cell peak. Sodium dodecyl sulfate slab gel electrophoresis and radioautography of 35S-methionine labeled cellular proteins confirmed that sorted cells are viable. Cells from the far left region contained increased amounts of labeled 18 Kd proglucagon and its 13-Kd and 10-Kd conversion intermediates, while cells from the right side were relatively enriched in labeled 12.4 Kd prosomatostatin. These results demonstrate that intrinsic light scattering alone can be used to prepare A- or D-cell enriched fractions from islets for biochemical analysis.
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PMID:Sorting of pancreatic islet cell subpopulations by light scattering using a fluorescence-activated cell sorter. 613 19

We have previously shown that stimulation of the preganglionic cervical sympathetic trunk leads to an acute increase in tyrosine hydroxylase (TyrOHase) activity in the rat superior cervical ganglion. This increase appears to be mediated in part by acetylcholine and in part by a second neurotransmitter. As a first step in an attempt to determine the identity of this noncholinergic transmitter, we have examined the ability of a number of neuropeptides to increase ganglionic TyrOHase activity in vitro. Secretin and vasoactive intestinal peptide (VIP) both stimulated TyrOHase activity, whereas angiotensin II, bombesin, bradykinin, cholecystokinin octapeptide, glucagon, insulin, luteinizing hormone-releasing hormone, [D-Ala(2), Met(5)]enkephalinamide, motilin, neurotensin, somatostatin, and substance P produced no effects. Secretin produced a significant increase in TyrOHase activity at 1 nM and a maximal elevation at 0.1 muM. VIP produced a significant increase at 0.1 muM and a near maximal effect at 10 muM. Although secretin was about 2 orders of magnitude more potent than VIP, it produced a significantly smaller maximal increase in enzyme activity. Incubation of ganglia with both secretin (10 muM) and VIP (10 muM) produced an increase in TyrOHase activity that was not significantly different from that produced by VIP alone. The stimulatory effects of secretin and VIP were reversible within minutes after removal of the peptides. Neither incubation of intact ganglia with the cholinergic antagonists hexamethonium and atropine nor prior decentralization of ganglia altered the response to the peptides. Thus, the data demonstrate that secretin and VIP acutely increase TyrOHase activity in the superior cervical ganglion and suggest that they produce this effect by acting directly on ganglionic neurons. It remains to be determined whether secretin or VIP or a related peptide is released during preganglionic nerve firing and whether one or more of these peptides is responsible for the noncholinergic elevation of TyrOHase activity produced by preganglionic nerve stimulation.
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PMID:Secretin and vasoactive intestinal peptide acutely increase tyrosine 3-monooxygenase in the rat superior cervical ganglion. 613 May 26

A specific glucagon antiserum was generated in rabbits using a derivatisation of the methionine residue in glucagon. A sensitive and specific assay for glucagon has been developed. Interference with the assay system by plasma factors was abolished by both extraction of plasma samples and the production of glucagon-free plasma for each individual.
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PMID:Radioimmunoassay for pancreatic glucagon based on specific derivatisation of the hormone. 616 95

Influence of amino acids upon pancreatic exocrine secretion has been investigated in the isolated perfused pancreas of rats. Arg produced significant and dose-related inhibition of pancreatic juice flow, protein output and amylase output evoked by CCK-PZ (1.25 pM). The secretory response evoked by CCK-PZ was inhibited by other amino acids (Ala, Asp, Asn, Gly, Ile, Leu, Lys, Met, Phe, Pro, Thr, Trp, Val, in each 20 mM). A similar inhibitory pattern was observed using 10 mixed amino acids of 2 mM each (Pro, Phe, Thr, Met, Lys, Asp, Leu, Trp, Val, Gly). Gly at a concentration of 20 mM produced significant inhibition of exocrine secretion evoked by ACh (50 nM) or GRP (36 pM). The inhibitory response induced by amino acids could not be repeated by using exogenous insulin (1 microM) and glucagon (280 nM). The inhibitory response was also not changed by increased extracellular Ca (5 or 10 mM). However, Gly (20 mM) produced inhibition of exocrine secretion evoked by Ca reintroduction into a pancreas which was pretreated with A 23187. It was suggested that the inhibitory effects of some amino acids on exocrine secretion are mainly caused by suppression of Ca influx in a stimulus-secretion coupling process.
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PMID:Inhibitory influence of amino acids on secretagogues induced exocrine secretion in isolated perfused rat pancreas. 620 12


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