Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between the thyrotropin (TSH) receptor and adenosine 3':5'-monophosphate (cyclic-AMP) dependent protein kinase activity in bovine thyroid plasma membrane fraction was investigated. After solubilization of thyroid plasma membranes, the molecular sizes of TSH binding protein and protein kinase activities were compared using the sucrose density gradient technique. Cyclic-AMP dependent protein kinase activity was present in a soluble thyrotropin receptor fraction. The Km of this enzyme was 2.2 x 10(-6) M for casein substrate in the absence or presence of 10(-5) M cyclic-AMP. A [3H]-cyclic-AMP binding protein was also found in this fraction. The Ka for cyclic-AMP binding was 0.11 x 10(6) M-1, with 3 nmoles per mg protein of total binding capacity. After fractionation using a continuous sucrose density gradient, one of the several [125I]-bovine TSH binding peaks corresponded to a [3H]-cyclic-AMP binding peak. After fractionation on a sucrose density gradient containing 0.4 M NaCl at pH 6.5, a major peak of protein kinase activity was stimulated by adding 10(-5) M cyclic-AMP. A peak of [3H]-cyclic-AMP binding activity corresponded to the same peak. Protein kinase activity in the receptor fraction was stimulated by adding 6 mg/ml bovine TSH. The soluble TSH receptor fraction also had an adenylate cyclase activity stimulated by TSH. These results suggest that some TSH receptors in thyroid plasma membranes have associated adenylate cyclase activity and cyclic-AMP dependent protein kinase activity. The receptor, cyclase, and kinase activities may exist in a functional primary receptor unit which is a component of thyroid plasma membranes.
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PMID:[Cyclic-AMP dependent protein kinase activity in the soluble thyrotropin receptor complex (author's transl)]. 624 85

We have developed a serum-free, chemically defined growth medium containing casein, insulin, transferrin, testosterone, and linoleic acid in Dulbecco's modified Eagle's medium/Ham's F12 medium, 1:1 (vol/vol), for growing murine T lymphomas. This medium supports the growth in suspension of all murine T lymphomas tested, including S49, WEHI 7, EL4, BW5147, and R1.1. Growth of these cell lines was maintained indefinitely with doubling times approaching those of cells grown in 10% (vol/vol) horse serum. This medium also supports the growth of several of the S49 variants of the beta-adrenergic receptor/adenylate cyclase/cyclic AMP/protein kinase pathway, suggeting little or no involvement of this pathway in the routine growth of S49 cells or in the mechanism of action of the factors in this defined medium. This serum-free medium should prove useful for studies of a variety of metabolic pathways and of differentiated functions of T-lymphoma cells.
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PMID:Growth of T-lymphoma cells in serum-free medium: lack of involvement of the cyclic AMP pathway in long-term cultures. 625 74

Exorphins, peptides with opioid activity, have previously been isolated from pepsin hydrolysates of alpha-casein [Zioudrou, C., Streaty, R. A., & Klee, W. A. (1979) J. Biol. Chem. 254, 2446-2449]. Analysis of these peptides shows that they correspond to the sequences 90-96, Arg-Tyr-Leu-Gly-Tyr-Leu-Glu, and 90-95, Arg-Tyr-Leu-Gly-Tyr-Leu, of alpha-casein. These peptides, as well as two of their analogues Tyr-Leu-Gly-Tyr-Leu-Glu (91-96) and Tyr-Leu-Gly-Tyr-Leu (91-95), have now been synthesized and characterized. Their opioid activity was examined by three different bioassays: (a) displacement of D-2-alanyl[tyrosyl-3,5-3H]enkephalin-(5-L-methioninamide) and [3H]dihydromorphine from rat brain membranes; (b) naloxone-reversible inhibition of adenylate cyclase in homogenates of neuroblastoma x glioma hybrid cells; (c) naloxone-reversible inhibition of electrically stimulated contractions of the mouse vas deferens. The synthetic peptide of sequence 90-96 was the most potent opioid in all three bioassays and its potency was similar to that of the isolated alpha-casein exorphins. The synthetic peptides were totally resistant to hydrolysis by trypsin and homogenates of rat brain membranes, but were partially inactivated by chymotrypsin and subtilisin. The difference in opioid activity of alpha-casein exorphins may be related to differences in conformational flexibility observed by NMR spectroscopy.
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PMID:Opioid activities and structures of alpha-casein-derived exorphins. 631 43

To explore the antisecretory effect of methylated casein (MC) cholera toxin was placed in isolated jejunal loops, and in vivo water fluxes were measured 3 h later in the presence or absence of MC. Secretion was observed in the loops filled with Ringer's solution only, but net absorption was observed in all 10 loops to which MC was added. Its actions was evident within 20 min, and was exerted directly on the luminal side of the epithelium. This response was dose-dependent and the antisecretory effect vanished after boiling MC and after ultrafiltration. In vitro, the antisecretory effect of MC consisted of reversing net Na and Cl fluxes from secretion to absorption (delta JNanet = 6.18 +/- 1.25 and delta JClnet = 5.10 +/- 1.66 microEq . h-1 . cm-2). This change was due to the enhancement of mucosal to serosal flux. Transepithelial potential difference and tissue conductance did not alter. Interestingly, MC did not interfere with intestinal function in the absence of stimulation by cholera toxin. In the presence of cholera toxin, MC and glucose both stimulated ionic absorption by different mechanisms, MC stimulating neutral NaCl absorption, and glucose stimulating electrogenic Na absorption. MC did not alter basal adenylate cyclase activity but it inhibited the cholera toxin-stimulated increase in activity. The present results indicate that methylated casein inhibits water and electrolyte secretion induced by cholera toxin in rat jejunum. Its availability, low cost, and curative effect from the luminal side constitute compelling indications for further investigation.
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PMID:Anticholeraic effect of methylated casein in rat jejunum. 651 35

Since the renal growth response to a high-protein diet is characterized by prominent hypertrophy of the medullary thick ascending limb of Henle's loop (MTAL), the functional and metabolic adaptations of this nephron segment to dietary protein were investigated. MTAL suspensions were obtained from rats fed equal amounts of isocaloric food containing either 10% (LP) or 32% (HP) casein for 4-6 weeks. The results show that intact MTAL of HP rats exhibit a blunted respiration rate, sodium pump activity, hormone-sensitive cAMP production and leucine oxidation rate in comparison with those of LP rats. On the other hand, adenylate cyclase and leucine transaminase activities, measured on permeabilized or homogenized MTAL, are enhanced by a HP diet. We conclude that the MTAL adapts to high dietary protein by increasing its maximal enzyme activities, but certain factors, present in intact cells, limit transport and metabolism in HP- more than in LP-fed rats. This reduced function per unit MTAL protein in HP rats is more than compensated for by hypertrophy of the MTAL tissue mass.
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PMID:Adaptation of the medullary thick ascending limb to dietary protein intake. 808 65

Maternal malnutrition leads to permanent alterations in insulin secretion of offspring and the soybean diet contributes to improve insulin release. At least a soy component, genistein, seems to increase the insulin secretion by activating the cAMP/PKA and PLC/PKC pathways. Here, we investigated the effect of the soybean diet on the expression of PKAalpha and PKCalpha, and insulin secretion in response to glucose and activators of adenylate cyclase and PKC in adult pancreatic rat islets. Rats from mothers fed with 17% or 6% protein (casein) during pregnancy and lactation were maintained with 17% casein (CC and CR groups) or soybean (SC and SR groups) diet until 90 days of life. The soybean diet improved the insulin response to a physiological concentration of glucose in control islets, but only in the presence of supra-physiological concentrations of glucose in islets from CR and SR groups. PMA also improved the insulin response in islets of SC and SR groups. The expression of PKCalpha was similar in all groups. Forskolin increased the insulin secretion; however, the magnitude of the increment was lower in islets from CR and SR groups than in control animals and in those from rats maintained with soybean diet than in rats fed with casein diet. The PKAalpha expression was similar between SR and CR groups and lower in SC than in CC islets. Thus, soybean diet improved the secretory pattern of beta cells, at least in part, by activating the cAMP/PKA-signaling cascade.
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PMID:Soybean diet improves insulin secretion through activation of cAMP/PKA pathway in rats. 1843 May 54


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