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)

Human adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) has been studied in preparations of fat cell membranes ("ghosts"). As reported earlier, under ordinary assay conditions (1.0 mM ATP, 5 mM Mg2+, 30 degrees C, 10 min incubation) the enzyme was activated 6-fold by epinephrine in the presence of the GTP analog, 5'-guanylyl-imidodiphosphate [GMP-P(NH)P] (Cooper, B. et al. (1975) J. Clin. Invest. 56, 1350-1353). Basal activity was highest during the first 2 min of incubation then slowed and was linear for at least the next 18 min. Epinephrine, added alone, was often without effect. but sometimes maintained the initial high rate of basal activity. GMP-P(NH)P alone produced inhibition ("lag") of basal enzyme early in the incubation periods. Augmentation of epinephrine effect by GMP-P(NH)P, which also proceeded after a brief (2 min) lag period, was noted over a wide range of substrate (ATP) concentrations. GTP inhibited basal levels of the enzyme by about 50%. GTP also allowed expression of an epinephrine effect, but only in the sense that the hormone abolished the inhibition by GTP. Occasionally a slight stimulatory effect on epinephrine action was seen with GTP. At high Mg2+ concentration (greater than 10 mM) or elevated temperatures (greater than 30 degrees C) GMP-P(NH)P alone activated the enzyme. Maximal activity of human fat cell adenylate cyclase was seen at 50 mM Mg2+, 1.0 mM ATP, pH 8.2, and 37 degrees C in the presence of 10(-4) M GMP-P(NH)P; under these conditions addition of epinephrine did not further enhance activity. Human fat cell adenylate cyclase of adults was insensitive to ACTH and glucagon even in the presence of GMP-P(NH)P.
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PMID:Human fat cell adenylate cyclase. Enzyme characterization and guanine nucleotide effects on epinephrine responsiveness in cell membranes. 0 40

The specificity of bovine spleen cathepsin B2 has been investigated by means of some natural oligo- and polypeptides, i.e. glucagon, melittin, insulin A and B chain, bradykinin, angiotensin I and II, oxytocin ACTH, clupein and salmin. The enzyme is primarily a carboxypeptidase which hydrolyzes peptide linkages of most amino acids common to proteins. In addition, cathepsin B2 displays amidase and esterase activity without requiring a free carboxyl group. The main pH optimum is between 4 and 5, in some cases higher.
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PMID:On the specificity of bovine spleen cathepsin B2. 1 11

Besides their well-known actions, glucagon, ACTH, pentagastrin and insulin from the APUD series exert a direct action on the bone calcium content. Incubation with these substances of rat calvaria in vitro yields an evident stimulation of osteolysis with ACTH. Pentagastrin inhibits osteolysis. Glucagon and insulin inhibit parathormone-stimulated osteolysis, with no influence on the spontaneous one. Glucagon, resembling calcitonin, stimulates the 45Ca uptake from the incubation medium. The action of these substances completes the series of hormones influencing bone calcium metabolism, underlining possible interference actions of APUD-type hormones.
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PMID:Effect of "APUD"-type hormones on osteolysis in vitro. 2 23

1. Adenylate cyclase (EC 4.6.1.1) activity was characterized in human liver, and its subcellular distribution compared with that of three other potential enzyme markers of the pericellular membrane: leucine aminopeptidase (EC 3.4.11.1), gamma-glutamyltransferase (EC 2.3.2.2) and 5'-nucleotidase (EC 3.1.3.5). Although these three enzyme activities were detected in each of the subcellular fractions studied, 85% of the total adenylate cyclase activity was found in the 1000 g pellet ('nuclear' fraction) with a threefold increase in specific activity as compared with the homogenate. No adenylate cyclase activity existed in the 150 000 g supernatant fraction. 2. In the 'nuclear' fraction, adenylate cyclase activity was increased in a dose-dependent fashion by glucagon with a half-maximal stimulation at 10 nmol/l and a maximal four- to seven-fold increase at 1 mumol/l. Catecholamines activated adenylate cyclase 2.5- to three-fold, with an order of potency (protokylol greater than isoprenaline greater than adrenaline greater than noradrenaline) typical of a beta 2-adrenoreceptor. Prostaglandin E1 and NaF also stimulated cyclase two- and four-fold respectively. Insulin, serotonin, dopamine, thyroid-stimulating hormone and ACTH had no effect. Adenosine provoked a weak inhibition at 0.1 mmol/l. Finally guanosine triphosphate and 5'-guanylyl imidodiphosphate induced a marked increase in basal activity, four- and eight-fold respectively, but both reduced the relative increase in enzyme activity due to glucagon or adrenaline. 3. Cyclase from foetal liver (12--16 weeks old) and cirrhotic adult liver appeared to behave similarly to that from normal liver; however, foetal cyclase was more active, and cirrhotic enzyme less active than normal adult liver. Both systems responded to catecholamines via a beta 2-adrenoreceptor. 4. These results validate the use of rat liver adenylate cyclase as a tool for pharmacological and physiological studies.
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PMID:The adenylate cyclase system in human liver: characterization, subcellular distribution and hormonal sensitivity in normal or cirrhotic adult, and in foetal liver. 4 65

The binding and degradation of insulin and glucagon to kidney cell membranes was examined. Time- and temperature-dependent specific binding of [125I]iodo-insulin to kidney cell membranes was demonstrated. The membranes also degraded insulin in a time-, temperature-, and protein concentration-dependent manner. The apparent Km of the degradation was 2.7 x 10(-7) M. Glucagon degradation by the kidney membranes was extremely active. Per milligram of protein the kidney membrane was over 20 times as active as the liver membrane. Even at 4 C, significant glucagon degradation occurred. Because of this very active degradation, glucagon binding could not be accurately assessed. The kidney glucagon-degrading activity was inhibited by glutahione and EDTA but unaffected by N-ethylmaleimide, ACTH, or insulin, all potent inhibitors of liver glucagon degradation. The apparent Km for glucagon degradation by the kidney, however, was essentially identical with that for the liver, 2.4 x 10(-6) M.
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PMID:Insulin and glucagon binding and degradation by kidney cell membranes. 10 82

Adult rats were rendered diabetic by a single iv injection of streptozotocin (70 or 75 mg/kg). In these rats, serum insulin fell to minimal levels during the 48 h following drug treatment, and this was roughly paralleled by a progressive decrease in the ability of the lung to oxidize glucose. The addition of insulin to diabetic rat lung slices in vitro had no restorative effect on the depressed glucose oxidative rate during a 2 h incubation period; however, two daily treatments of the rats with 1 unit of protamine, zinc insulin completely restored lung glucose oxidation rate to normal, without significantly reducing the hyperglycemic state of the rats. An examination of the temporal changes in glucose utilization by the rat lung after acute insulin treatment revealed that the diabetic lung responded directly to serum levels of insulin, whereas the normal lung appeared to be unaffected by serum insulin levels as hihg as 87 ng/ml. The reduced rate of glucose oxidation in the diabetic lung was apparent after perfusion of the lung with glucose-free medium, and was characterized by a significant reduction in Vmax without an alteration in Km. This was attended by a depressed ability of the lung to incorporate [3H]leucine into protein and an increased ability to produce lactate, but hexose monophosphate shunt activity was normal. Specific receptors for insulin have been identified and partially characterized in crude membrane preparations of normal rat lung. The interaction of insulin with these receptors was rapid, reversible, saturable, and was dependent upon time and temperature. The binding of labeled insulin was inhibited by low concentrations of unlabeled insulin and by high concentrations of proinsulin, whereas it was unaffected by the presence of glucagon, gastrin, prolactin, ACTH, or growth hormone in microgram amounts. These observations suggest that insulin regulates the transport and utilization of glucose in the rat lung, and that this tissue contains specific receptors for insulin.
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PMID:Pulmonary insulin responsivitiy: in vivo effects of insulin on the diabetic rat lung and specific insulin binding to lung receptors in normal rats. 14 46

Rat liver membrane adenylate cyclase (EC 4.6.1.1) that has been stimulated more than 10-fold by cholera toxin (choleragen) has a 3-fold greater sensitivity to stimulation by glucagon. Choleragen similarly increases the sensitivity of cyclase to other peptide (ACTH, vasoactive intestinal polypeptide) and nonpeptide (catecholamines) hormones in this and other tissues. The rate of 125I-labeled glucagon-membrane dissociation is decreased about 2-fold in toxin-treated liver membranes. Toxin-activated cyclase activity of fat cell membranes is retained upon solubilization with Lubrol PX. Provided 125I-labeled choleragen is first incubated with cells under conditions resulting in enzyme activation, the solubilized cyclase activity migrates with a component of 125I-labeled choleragen on gel filtration chromatography. Agarose derivatives containing the "active" subunit (molecular weight 36,000) of the toxin can specifically adsorb solubilized adenylate cyclase. Toxin-stimulated cyclase can be immunoprecipitated with antitoxin or anti-"active" subunit antibodies. There is a large excess of membrane receptors (ganglioside GM1) which, with the use of choleragenoid, can be shown to be functionally equivalent with respect to cyclase activation. Choleragenoid, an inactive competitive antagonist of toxin binding, can occupy and block a large proportion of toxin receptors without affecting toxin activity. A scheme of toxin action is proposed that involves lateral membrane diffusion of the initially inactive toxin-receptor complex with subsequent direct interaction with and modulation of adenylate cyclase. The basic features of this scheme may be pertinent to the mechanisms by which hormone receptors normally modulate adenylate cyclase.
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PMID:Mechanism of action of cholera toxin and the mobile receptor theory of hormone receptor-adenylate cyclase interactions. 16 20

The effect of injection of glycogenolytic enzymes on tissue glycogen, blood glucose and plasma insulin was studied in mice. No effects were observed following phosphorylase, whereas the hydrolytic enzymes, alpha-amylase and acid amyloglucosidase depressed liver glycogen. In addition acid amyloglucosidase induced a decrease in blood glucose, a slight elevation of plasma insulin and a marked increase in tolbutamide-stimulated insulin release. At the doses given none of the enzymes affected muscle glycogen. Amyloglucosidase pretreatment markedly enhanced insulin release induced by glibenclamide, leucine, isoleucine, lysine and glucose whereas insulin release stimulated by IPNA, ACTH, glucagon and "CCK-PZ" was unaffected. Injection of acid amyloglucosidase has a profound influence on carbohydrate content and regulation in mice. It is suggested that the dependence or independence of amyloglucosidase activity among the insulin secretagogues tested might reflect different or partially different mechanisms in the process of insulin secretion.
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PMID:Carbohydrate content and regulation following injection of different glycogenolytic enzymes. 16 77

Insulin action is discussed with emphasis on events that occur at the plasma membrane. A summary is presented of previous studies which indicate that the insulin receptor of fat and liver cells is a large glycoprotein, partially buried in the outer surface of the plasma membrane, with a high (K-D approximately 10-10 M) and specific affinity for insulin. The participation of membrane phospholipids in the binding of insulin and the role of sialic acid residues in the transmission of the insulin binding signal are discussed. The relation of insulin action to its effects on cyclic nucleotide levels is explored. On the one hand, insulin action (glucose transport) is inhibited by compounds (cholera toxin, ACTH, glucagon and L-norepinephrine) that stimulate adenylate cyclase; conversely, insulin both inhibits the lipolytic action of these compounds, and raises cellular levels of cyclic GMP. An hypothesis is presented whereby a single cyclase species may be responsible for the formation of either cyclic AMP or cyclic GMP, depending on the nature of the hormone stimulus. The role of membrane phosphorylation in the action of insulin is discussed in the context of experiments demonstrating a specific inhibition by ATP of insulin-mediated glucose transport, in association with the phosphorylation of two specific membrane proteins. The ability of insulin to modulate cyclic nucleotide levels in cultured cells and to act as a growth factor is discussed. Insulin stimulates DNA synthesis and the uptake of alpha-aminoisobutyric acid in human fibroblasts, which effects are also mediated by epidermal growth factor. Insulin acts at concentrations much higher than those obtained in vivo, whereas epidermal growth factor acts at concentrations thought to be physiological. The insulin binding sites (K-D is approximately equal to 10-9 M) related to growth, and observed both in human fibroblasts and in lectin-stimulated and leukemic human lymphocytes would not be appreciably occupied at physiological insulin concentrations. The implications of such 'low affinity' binding sites for insulin are discussed in relation to the action of other growth factors.
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PMID:Insulin: interaction with membrane receprots and relationship to cyclic purine nucleotides and cell growth. 16 82

Twenty-four endocrine pancreatic tumors were examined immunohistochemically for insulin, glucagon, gastrin and ACTH. In seven of these tumors, more than one peptide-hormone-containing cell type was observed. These seven tumors were also examined with conventional staining methods for the presence of A1, A2, and B cells. The results showed that these staining methods do not always distinguish between the different hormone-producing cell types of endocrine pancreatic tumors. In spite of the fact that several types of hormone-secreting cells were found in the tumors, the case histories described symptoms characteristic of hypersecretion of only one of the hormones. The hormone of the predominating cell type could not always explain the clinical symptoms. Our results indicate the endocrine pancreatic tumors often are multihormonal. Therefore, it would seem advisable to screen serum from all insuloma patients for a variety of peptide hormones.
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PMID:Mixed endocrine pancreatic tumors producing several peptide hormones. 16 86


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