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)

Our previous studies on carbohydrate structures of purified porcine spleen cathepsin B indicated that there are two cathepsin B isozymes, each containing a different carbohydrate (Takahashi, T., Schmidt, P.G., and Tang, J. (1984) J. Biol. Chem. 259, 6059-6062). We have now isolated these two enzymes and carried out a comparative study on their structures and enzymic properties. The major isozyme (CB-I) is a two-chain enzyme (Mr = 28,000) with a light chain (Mr = 5,000) and a heavy chain (Mr = 23,000), whereas the minor enzyme (CB-II) is a single chain enzyme (Mr = 27,000). The NH2-terminal amino acid residues of CB-I were leucine and valine for the light and heavy chain, respectively. However, the NH2-terminal residue of CB-II was not available for automated Edman degradation. In addition, peptide mapping experiments indicated a difference in the primary structure of these two proteins. Despite such structural differences, they are similar in many enzymic properties. CB-I was more catalytically efficient than CB-II toward synthetic substrates, except for the substrate benzoyl-L-arginine beta-naphthylamide for which the relative catalytic efficiency is reversed. Both isozymes degraded glucagon by a dipeptidyl carboxypeptidase activity. Under the same conditions, CB-I was 4-5 times more efficient than CB-II. The results indicate that the cathepsin B isozymes are two separate gene products, but they are similar in enzymic properties.
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PMID:Comparative studies of two cathepsin B isozymes from porcine spleen. Isolation, polypeptide chain arrangements, and enzyme specificity. 372 2

Recently, a putative hormone, glucagon-like peptide I (GLP I), has been identified in the predicted sequences of the precursors to pancreatic glucagon in human, rat, hamster, and ox. The distribution of GLP I immunoreactivity in canine and feline pancreas and gastrointestinal tract was examined immunohistochemically and was compared with that of two other antigenic determinants of pancreatic pro-glucagon, i.e., glucagon and the NH2 terminus of glicentin. All three determinants occurred in the same population of islet cells in normal pancreas and in pancreas consisting predominantly of islet tissue from dogs with canine pancreatic acinar atrophy. Northern blot analysis of mRNA from the latter tissue, using a rat pre-pro-glucagon complementary DNA probe, revealed a single mRNA species similar in size to the pre-pro-glucagon mRNA detected in fetal rat pancreas. The three antigenic determinants of pancreatic pro-glucagon were co-localized also in intestinal L-cells and in canine gastric A-cells. Canine and feline pancreatic pro-glucagons therefore resemble those identified in other mammals and may also occur in gastrointestinal endocrine cells. Although there is evidence that the GLP I sequence is not liberated from pancreatic pro-glucagon, our results raise the possibility that this putative hormone may be a cleavage product of pro-glucagon in the gastrointestinal tract.
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PMID:Distribution of glucagon-like peptide I in canine and feline pancreas and gastrointestinal tract. 375 50

Induction of cardiac work increased protein synthesis in hearts supplied glucose or a mixture simulating normal plasma levels of glucose, insulin, glucagon, lactate, and beta-hydroxybutyrate. During 2 h of perfusion, cardiac work did not accelerate protein synthesis in hearts supplied a mixture of glucose, lactate, and higher concentrations of insulin. Protein degradation was decreased by work in hearts supplied glucose. Nitrogen balance was negative in Langendorff-perfused hearts provided glucose, but was less so in working preparations. Nitrogen balance was zero or positive in working hearts provided the mixture simulating plasma or the mixture of glucose, lactate, and insulin. In Langendorff preparations, increased aortic pressure accelerated protein synthesis during the second hour of perfusion in hearts supplied glucose, glucose plus insulin, or pyruvate. When ventricular pressure development was prevented by ventricular draining or when drained hearts were arrested with tetrodotoxin, protein synthesis still increased as perfusion pressure was raised from 60 to 120 mm Hg. Oxygen consumption increased as aortic pressure was increased in drained, beating hearts, but was unaffected in arrested, drained hearts. These studies indicated that increased aortic pressure and its attendant stretch of the ventricular wall were the mechanical parameter most closely associated with faster rates of protein synthesis.
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PMID:Mechanical factors affecting protein turnover in isolated rat hearts. 375 75

Elevated plasma ammonia level in hepatic cirrhosis has been attributed to a lack of conversion of enteric ammonia into urea or to its entry into systemic circulation via portasystemic shunting, or to both. It is exaggerated by excessive protein intake. Because hyperglucagonemia is well documented in cirrhosis and a protein meal is an effective glucagon secretagogue, plasma glucose, insulin, glucagon, and ammonia levels were determined in 50 cirrhotic patients after an overnight fast. Effects of a protein meal were also assessed in 20 of these patients. Plasma glucose was normal and remained unaltered after a protein meal. Insulin, glucagon, and ammonia levels were elevated, but only in patients with advanced liver dysfunction. Ammonia levels correlated significantly with glucagon (r = 0.61, p less than 0.001), but not with insulin or glucose levels. Insulin and glucagon levels rose after a protein meal in all patients and controls; whereas a significant rise in the ammonia level occurred only in decompensated cirrhotics. Elevation of the ammonia level was significantly correlated with fasting glucagon (r = 0.54, p less than 0.05), as well as with glucagon response (r = 0.65, p less than 0.01), but not with basal insulin or insulin response. Furthermore, the rise in ammonia level occurred too early to be accounted for by enteric generation. Finally, direct effects of glucagon administration on plasma glucose and serum ammonia were examined in 15 cirrhotic patients. Glucose response was significantly blunted in cirrhotic patients as compared with normal subjects, whereas serum ammonia rose promptly but only in cirrhotics, with maximum rise being noted in cirrhotic patients with advanced liver dysfunction. This study, therefore, suggests that hyperglucagonemia may contribute significantly to hyperammonemia in hepatic cirrhosis.
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PMID:Elevated plasma ammonia level in hepatic cirrhosis: role of glucagon. 388 8

We have developed a reverse-phase HPLC method to purify 125I-labeled products resulting from the chloramine-T-based iodination of glucagon and have used the products [(125I)iodoTyr13]glucagon, [(125I)iodoTyr10,13]glucagon, and [(125I)iodoTyr10]glucagon) to study the receptor binding of glucagon and the cell-mediated metabolism of the hormone by isolated canine hepatocytes. The extent of binding of the three labeled glucagons to cell receptors differed at steady state (8.5, 11.9, and 12.6% of the three peptides, respectively, becoming cell-associated), but each of the labeled glucagons approached steady state binding at the same rate. Further, unlabeled glucagon competed for the binding of each of the labeled peptides in parallel under steady state conditions, and each of the peptides showed potent activity in inhibiting [14C]fructose incorporation into glycogen. Gel filtration of the acetic acid-extracted, cell-associated products of radiolabeled glucagon binding revealed 10-20% of the material as a shoulder on the descending limb of the peak of hormone for each of the three labeled peptides. Trypsin digestion of the lower molecular weight peptide derived from [(125I)iodoTyr13]glucagon resulted in a fragment containing residues 13 to 17 as the only detectable radiolabeled product. On the other hand, trypsin digestion of the analogous peptide derived from [(125I)iodoTyr10]glucagon revealed, in addition to the radiolabeled fragment containing residues 1 to 12, a major fragment identified by radiosequence analysis to contain residues 4 to 12 and a minor fragment identified to contain residues 7 to 12. We conclude that (a) notwithstanding apparent differences in affinities exhibited by [(125I)iodoTyr13]glucagon, [(125I)iodoTyr10,13]glucagon, and [(125I)iodoTyr10]glucagon for binding to canine hepatocytes, the interactions of all three peptides with the glucagon receptor are functionally equivalent, and (b) the cell-mediated metabolism of receptor-bound glucagon involves the formation of hormone-derived peptides in which the biologically important NH2-terminal region of the hormone has been modified by limited proteolytic cleavage.
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PMID:Receptor binding and cell-mediated metabolism of [125I]monoiodoglucagon by isolated canine hepatocytes. 608 19

Aromatic position 4 somatostatin (SS) analogs were synthesized by solid phase methodology and assayed in vivo for their effects on pentobarbital-stimulated GH levels in fed rats and insulin and glucagon levels in fasted rats. [F5-Phe4]SS was approximately 3 times more active than somatostatin in inhibiting all three hormones. [Phe4,D-Trp8]SS inhibited GH about 4 times more effectively than somatostatin and was only twice as active as somatostatin in the pancreas. [rho-NH2-Phe4]SS exhibited strong selectivity toward inhibition of GH, being 4 times more potent than somatostatin in the pituitary while only about 40% as active in the pancreas. [rho-NH2-Phe4,D-Trp8]SS maintained this same degree of selectivity toward GH inhibition and exhibited a striking 15-fold increase in activity in the pituitary compared to somatostatin. All four analogs inhibited GH for a longer period of time than somatostatin when administered sc at a dose of 10 microgram/100 g BW. [rho-NH2-Phe4,D-Trp8]SS was the longest acting of these analogs, with approximately a 2-h duration of inhibition of GH. [Phe4]SS, administered iv at a dose of 50 microgram/100 g BW, also inhibited GH for approximately 2 h. These data further support the feasibility of developing long-acting somatostatin analogs with selectivity toward a given hormone.
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PMID:Potent, highly selective inhibition of growth hormone secretion by position 4 somatostatin analogs. 611 51

FMRF-NH2-like immunoreactivity was localized in the pancreatic polypeptide containing cells of the rat islet. FMRF-NH2 was investigated with regard to its effect on insulin, somatostatin and glucagon secretion from the isolated perfused rat pancreas. FMRF-NH2 (1 microM) significantly inhibited glucose stimulated (300 mg/dl) insulin release (p less than 0.005) and somatostatin release (p less than 0.01) from the isolated perfused pancreas. FMRF-NH2 (1 and 10 microM) was without effect on glucagon secretion, either in low glucose (50 mg/dl), high glucose (300 mg/dl), or during arginine stimulation (5 mM). These findings indicate that these FMRF-NH2 antisera recognize a substance in the pancreatic polypeptide cells of the islet which may be capable of modulating islet beta and D cell activity.
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PMID:Phe-met-arg-phe-amide (FMRF-NH2) inhibits insulin and somatostatin secretion and anti-FMRF-NH2 sera detects pancreatic polypeptide cells in the rat islet. 614 24

The semi-synthetic approach has been used to obtain new analogs of the peptide hormone glucagon. Using the highly purified 27 amino acid fragment of cyanogen bromide-treated glucagon, we have prepared, by nucleophilic addition to the lactone ring, the following derivatives: CNBr-Gly28-glucagon, CNBr-glucagon hydrazide, CNBr-glucagon n-butylamide and CNBr-glucagon biotinamide. Direct aminolysis of the lactone was successful only with sterically unhindered primary amines. Addition of an amino acid could be accomplished by formation of the peptide hydrazide followed by azide coupling. All these analogs were full agonists with decreased potency relative to the native hormone. Examination of the structure-function relationships of these new C-terminal glucagon derivatives suggests that the hydrophobic side-chain of methionine is important to the binding of glucagon to its receptor and that the C-terminal portion of glucagon is only involved in the binding of the hormone to the receptor and not in the transduction process.
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PMID:Preparation and properties of glucagon analogs prepared by semi-synthesis from CNBr-glucagon. 624 92

1. The relationship between urea synthesis, intracellular N-acetylglutamate and the capacity of rat-liver mitochondria to synthesize citrulline was investigated. 2. Treatment of rats with glucagon prior to killing results not only in an increased intramitochondrial ATP concentration and an increased capacity of the mitochondria to synthesize citrulline, but also in an increased concentration of intramitochondrial N-acetylglutamate. 3. Comparison of the rate of citrulline synthesis in mitochondria from glucagon-treated and from control rats, incubated under different conditions, shows that the increased N-acetylglutamate concentration after glucagon treatment is at least in part responsible for the observed increased capacity of the mitochondria to synthesize citrulline. 4. Ureogenic flux in isolated hepatocytes under different incubation conditions correlated with the intracellular concentration of N-acetylglutamate and with the capacity of the mitochondria to synthesize citrulline. 5. When isolated hepatocytes were incubated with NH3, ornithine, lactate and oleate, intracellular N-acetylglutamate increased about eightfold in the first 10 min; during this period the rate of urea synthesis increased considerably. 6. It is concluded that the concentration of intramitochondrial N-acetylglutamate plays an important role in the short-term control of flux through the urea cycle under different nutritional and hormonal conditions.
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PMID:The relationship between intramitochondrial N-acetylglutamate and activity of carbamoyl-phosphate synthetase (ammonia). The effect of glucagon. 624 85

The ability of several chemically modified forms of glucagon to activate adenylate cyclase have been compared with their ability to displace 125I-glucagon from specific membrane binding sites. The results demonstrate that both NH2-terminal and COOH-terminal portions of the peptide, as well as the central region of the glucagon molecule, are all involved in receptor binding and subsequent activation of adenylate cyclase. Receptor binding was very sensitive to chemical modification of the polar residues of glucagon. For example, conversion of the sole lysine residue of glucagon to homoarginine resulted in over a 2-fold loss in receptor-binding affinity. Loss in ability to activate adenylate cyclase was at least as great as loss in receptor binding for all of the derivatives. In the case of derivatives modified at the COOH terminus, the loss in ability to activate adenylate cyclase correlated well with loss in receptor binding. In general, however, the loss of the ability to activate adenylate cyclase was greater than the loss in binding affinity. This difference was greatest for the derivative N alpha-trinitrophenyl glucagon where the loss in adenylate cyclase activation was about 100-fold greater than the loss in receptor binding. This derivative behaved as an antagonist to glucagon in the activation of adenylate cyclase.
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PMID:Structural requirements for glucagon receptor binding and activation of adenylate cyclase in liver. Study of chemically modified forms of the hormone, including N alpha-trinitrophenyl glucagon, an antagonist. 625 84


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