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)

The insulinotropic and glucagon-releasing activity of acid extracts of rat hypothalami were tested in two bioassay systems using short-time incubation of isolated rat pancreatic islets and a rat insulinoma (RIN) cell line. Release of insulin and glucagon into the incubation medium was measured by radioimmunoassay. The major insulin-releasing and glucagon-releasing activity eluted in a broad zone in Sephacryl S-200 gel filtration in 30% acetic acid corresponding to the molecular weights between approximately 10 and 40 kD. The highest activity was eluted in a zone corresponding to 14 kD and was purified to homogeneity by means of two steps of reversed-phase HPLC. Amino acid analysis and SDS polyacrylamide gel electrophoresis indicated that the biologically active material was the rat small (myelin) basic protein characterized previously by Dunkley & Carnegie (1974). The purified rat hypothalamic material showed insulinotropic and glucagon-releasing activity indistinguishable from that of purified porcine myelin basic protein, and lost its insulinotropic activity when incubated with anti-myelin basic protein immunosorbent. We conclude that the major insulin-releasing and glucagon-releasing activity in acid extracts of the high-molecular-weight fractions of rat hypothalami is myelin basic protein.
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PMID:Myelin basic protein present in the acid extracts of rat hypothalami releases insulin and glucagon from isolated rat pancreatic islets. 246 73

A protein that inactivates the immunoreactivity of GnRH, TRH and angiotensin II has been isolated from human term placentae. Only in the presence of DTT, a sulphydryl agent, are OXY and SRIF also inactivated by this protein. However, it is without effect on CRF, hCS, or hCG. It also inhibits the biological activity of GnRH, i.e. its ability to stimulate pituitary LH and FSH. The ability of this protein to inactivate GnRH, TRH or angiotensin II can be inhibited by various peptidase inhibitors. Thus, we have postulated that it is a chorionic peptidase, specific for these peptides, and herein called chorionic peptidase-1 (C-ase-1). Isolation of this protein, C-ase-1, has been effected using permeation, ion exchange and affinity chromatography. As estimated by SDS-PAGE and HPLC analyses, C-ase-1 has an apparent molecular weight of 58,000. It is proposed that C-ase-1 may be an important chorionic regulator of GnRH, TRH and angiotensin II levels during pregnancy.
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PMID:Characterization and purification of a placental protein that inactivates GnRH, TRH and angiotensin II. 250 48

[125I]VIP (vasoactive intestinal peptide) bound to apical membranes isolated from the bovine tracheal epithelium with a half maximal inhibition by unlabeled VIP (IC50) of 0.6 x 10(-9)M and binding was reversible. Glucagon did not affect [125I]VIP binding to the membranes. [125I]VIP was covalently cross-linked to tracheal membrane proteins using disuccinimidyl suberate. SDS-polyacrylamide gel electrophoresis of labeled tracheal membranes revealed one major [125I]-receptor complex of Mr = 71,000 to which binding of [125I]VIP was inhibited by 10 microM unlabeled VIP. These results are consistent with the presence of a specific, high-affinity receptor for VIP, with a Mr = 71,000, in apical membrane vesicles isolated from the bovine tracheal epithelium.
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PMID:Evidence for vasoactive intestinal peptide receptors in apical membranes from tracheal epithelium. 253 97

125I-Labelled glucagon-like peptide-1(7-36)amide was cross-linked to a specific binding protein in plasma membranes prepared from RINm5F rat insulinoma-derived cells using disuccinimidyl suberate. Consistent with the presence of a single class of binding site on the surface of intact cells, only a single radiolabelled band at Mr63,000 was identified by SDS-PAGE after solubilization of the ligand-binding protein complex. The band was not observed when 10nM glucagon-like peptide-1(7-36)amide was included in the binding assay, but 1 microM concentrations of glucagon-like peptide-1(1-36)amide, glucagon-like peptide-2 and glucagon did not decrease the intensity of labelling. No change in the mobility of the band was observed under reducing conditions, suggesting that the binding protein in the receptor is not attached to other subunits via disulphide bonds. In control incubations using plasma membranes from pig intestinal epithelial cells, which do not contain specific binding sites for glucagon-like peptide-1(7-36)amide, no cross-linked ligand-binding protein complex was observed.
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PMID:Characterization of the receptor for glucagon-like peptide-1(7-36)amide on plasma membranes from rat insulinoma-derived cells by covalent cross-linking. 255 26

Receptor binding assays demonstrate that bovine parathyroid hormone (PTH) and human PTH(1-34) can displace [125I]iodoglucagon from binding to its receptor in rat liver plasma membranes. The displacement of [125I]iodoglucagon requires several thousand-fold more bovine PTH or human PTH(1-34) than glucagon. However, the PTH peptides are more effective than secretin, which up to a concentration of 10(-5) M exhibits no ability to displace [125I]iodoglucagon. The greater potency of PTH compared with secretin occurs despite the fact that secretin shows a great deal of sequence homology with glucagon while PTH shows none. We demonstrate by circular dichroism that in the presence of 3 mM SDS glucagon and hPTH(1-34) have similar secondary structure contents, while secretin is more helical. Our results suggest that receptors can recognize gross conformational features of a peptide hormone in addition to interacting with a specific amino acid sequence. The ability of PTH to interact with glucagon receptors can be modulated by incorporation of charged amphiphiles into the plasma membrane. Negatively charged taurodeoxycholic acid increases the binding of the more cationic PTH while positively charged myristyltrimethylammonium bromide decreases this interaction. These effects demonstrate that receptor specificity can be modulated by its lipid environment and that electrostatic interactions between the hormone and the membrane surface can contribute to receptor binding.
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PMID:Conformational determinants in receptor recognition of peptide hormones: interaction of parathyroid hormone with the glucagon receptor. 303 Aug 52

Hepatocytes were isolated by application of the two-step collagenase perfusion technique to pieces of human liver. Hepatocytes were cultivated in serum-free medium or 10% fetal calf serum medium supplemented with insulin, glucagon and dexamethasone. The cells were kept in culture for up to 16 days and 75% of the medium was regularly changed. Fibronectin in culture medium was detected by means of an ELISA with an assay range of 2.2-560 micrograms/l. The interassay imprecision was 6.3% at 500 micrograms/l and 14.3% at 10 micrograms/l. Significant amounts of fibronectin were detected in all cultures. During culture, fibronectin accumulated in the medium and the quantity secreted by hepatocytes by far exceeded the amounts of fibronectin associated with hepatocytes prior to cultivation. Maximum secretion rate by 10(6) hepatocytes was 167.5 +/- 73.3 ng fibronectin (mean +/- SEM, n = 3) in 24 h. When analysed by means of SDS-PAGE and immunoblotting the fibronectin isolated from hepatocyte culture medium and cell lysate co-migrated with fibronectin obtained from plasma. Our data show, for the first time, that human hepatocytes synthesize and secrete fibronectin, and it is suggested that the human liver is an important source of plasma fibronectin.
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PMID:Human hepatocytes in culture synthesize and secrete fibronectin. 320 Nov 2

A proteinase from the venom of Vipera lebetina was purified by chromatography on Sephadex G-100 and CM-cellulose. The purified proteinase was homogeneous on SDS-polyacrylamide gel electrophoresis and consisted of a single chain with molecular weight of 37,000 +/- 1500. The isoelectric point of the proteinase was over 10. The enzyme was active on casein but not on esters and amides of arginine. It split the oxidized insulin B-chain at the peptide bonds of Tyr16-Leu17, Phe24-Phe25 and Phe25-Tyr26, and glucagon at the bonds Tyr10-Ser11, Leu14-Asp15 and Leu26-Met27. The enzyme was inhibited by DFP and PMSF, and partially by soybean trypsin inhibitor, but not with EDTA.
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PMID:Purification and properties of a proteinase from Vipera lebetina (snake) venom. 330 28

Intravenous injection of high doses of bacterial derived growth hormone (1 and 2 mg Somatonorm) did not affect the plasma levels of glucagon, insulin and free fatty acids in fasted and fed rabbits. On the other hand, 1 and 2 mg human extracted growth hormone (Crescormon) had stimulatory effects on plasma levels of glucagon, insulin and free fatty acids. These results indicate that the observed stimulatory effects in the rabbits were not due to the growth hormone molecule itself. It was shown by gel filtration and SDS electrophoresis that Crescormon contained constituents that were not present in Somatonorm. The differences in the observed metabolic effects of bacterial derived and pituitary growth hormone preparations in the rabbits could possibly be attributed to a human pituitary lipid-mobilizing factor LMF.
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PMID:Different acute in vivo effects of bacterial derived and pituitary growth hormone preparations on plasma levels of glucagon, insulin and free fatty acids in rabbits. 388 38

Ostrich serum albumin (OsSA) was purified by a combination of heat fractionation and polyethylene glycol precipitation. Equilibrium centrifugation revealed a relative molecular mass of 71,666 for the purified monomer, whereas the presence of a dimeric form was confirmed by means of PAGE and SDS-PAGE analysis. Compared to other species, relatively high levels of proline, glycine, isoleucine and histidine together with lowered amounts of half cystine, phenylalanine and arginine were observed in OsSA. A single N-terminal aspartic acid was identified. Isolated chicken adipocytes revealed a significantly lower in vitro lipolytic responsiveness towards added glucagon when OsSA replaced bovine serum albumin (BSA) in the medium (Km = 6.359 and 1.135 nM, Vm = 36.70 and 46.72 nmol/hr/micrograms adipocyte DNA for OsSA and BSA respectively).
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PMID:The isolation and characterization of serum albumin from the ostrich (Struthio camelus). 409 40

The hepatic glucagon receptor was covalently labeled with [125I-Tyr10]-monoiodoglucagon by use of the heterobifunctional crosslinker hydroxysuccinimidyl-p-azidobenzoate and analyzed by SDS-gel electrophoresis. The autoradiogram of the gel showed one band at Mr = 63,000 that was sensitive to excess unlabeled glucagon and GTP. The labeled receptor was solubilized with Lubrol-PX and the hydrodynamic characteristics of the receptor were determined. The molecular parameters of the solubilized receptor are S20,w = 4.3 +/- 0.1, Stokes radius = 6.3 +/- 0.1 nm, frictional coefficient f/f degrees = 1.8 and a calculated Mr = 119,000. Incubation of liver membranes at 32 degrees for 15 min prior to the addition of [125I-Tyr10] permitted us to identify the high molecular weight form (Mr approximately equal to 113,000) by direct SDS-gel electrophoretic analysis. Limited elastase treatment of the hormone-occupied receptor results in the appearance of a Mr = 33,000 fragment, that retains guanine nucleotide sensitivity. Elastase treatment of vacant receptors results in a Mr = 24,000 fragment that binds hormone in a GTP-sensitive manner. The Mr = 24,000 fragment is contained within the Mr = 33,000 fragment. The Mr = 63,000 receptor upon treatment with endo-beta-N-acetylglucosamine F for 4 h yields four fragments of apparent Mr = 61,000, 56,000, 51,000, and 45,000; 24 h treatment results in the accumulation of the last two fragments. Neither Mr = 33,000 and 24,000 fragment appear to be substrates for endo-beta-N-acetylglucosaminidase F. These data allow us to conclude that the hepatic glucagon receptor in the membrane is a dimer of approximately 60,000 dalton hormone binding subunit which is a glycoprotein containing at least four N-linked glycans accounting for 18,000 daltons of its mass. Both the hormone binding function and the capacity for the interaction with the stimulatory regulator of adenylyl cyclase are contained within a fragment of only approximately 21,000 daltons that does not contain any N-linked glycans.
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PMID:Characterization of the hepatic glucagon receptor. 609 55


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