Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Subcellular distribution of the enzymes related to the cellular action of antidiuretic hormone was studied in bovine renal medulla. The highest activity of vasopressin-stimulated adenylate cyclase was found in plasma membranes. The basal activity increased two times above homogenate while vasopressin-stimulated and NaF-stimulated activities both increased five times. Adenylate cyclase activity was present also in other particulate fractions, but it was not significantly stimulated by vasopressin. Cyclic AMP phosphodiesterase was predominantly located in the cytosol when assayed with 0.5 mM cyclic AMP or with 5 muM cyclic AMP. However, with the latter concentration of cyclic AMP more activity remained associated with the particulate fractions and was more inhibited by theophylline. The highest cyclic AMP-stimulated protein kinase activity occurred in the cytosol. Protein kinase activity present in other subcellular fractions was not markedly stimulated by cyclic AMP. Protein phosphatase activity was highest in cytosol when assayed using 32P-histones, 32P-plasma membrane proteins, and 32P-cytoslic proteins. The activity was unaffected by 10-6M to 10-4M cyclic AMP or cyclic GMP. The activity was completely inhibited by 10mM ZnSO4 and 10mM CuSO4; 10mM NaF inhibited the activity by approximately 14%. The enzymes related to the cellular action of vasopressin are predominatly localized in the cytosol except for the vasopressin-sensitive adenylate cyclase which is plasma membrane bound. To mediate the effect of antidiuretic hormone and act on the luminal plasma membrane these soluble enzymes and their substrates should be compartmentalized, possibly by a system of cytoplasmic microtubules.
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PMID:Subcellular distribution of the enzymes related to the cellular action of vasopressin in renal medulla. 16 75

In fat cells isolated from the parametrial adipose tissue of rats, the addition of purified adenosine deaminase increased lipolysis and cyclic adenosine 3':5'-monophosphate (cyclic AMP) accumulation. Adenosine deaminase markedly potentiated cyclic AMP accumulation due to norepinephrine. The increase in cyclic AMP due to adenosine deaminase was as rapid as that of theophylline with near maximal effects seen after only a 20-sec incubation. The increases in cyclic AMP due to crystalline adenosine deaminase from intestinal mucosa were seen at concentrations as low as 0.05 mug per ml. Further purification of the crystalline enzyme preparation by Sephadex G-100 chromatography increased both adenosine deaminase activity and cyclic AMP accumulation by fat cells. The effects of adenosine deaminase on fat cell metabolism were reversed by the addition of low concentrations of N6-(phenylisopropyl)adenosine, an analog of adenosine which is not deaminated. The effects of adenosine deaminase on cyclic AMP accumulation were blocked by coformycin which is a potent inhibitor of the enzyme. These findings suggest that deamination of adenosine is responsible for the observed effects of adenosine deaminase preparations. Protein kinase activity of fat cell homogenates was unaffected by adenosine or N6-(phenylisopropyl)adenosine. Norepinephrine-activated adenylate cyclase activity of fat cell ghosts was not inhibited by N6-(phenylisopropyl)adenosine. Adenosine deaminase did not alter basal or norepinephrine-activated adenylate cyclase activity. Cyclic AMP phosphodiesterase activity of fat cell ghosts was also unaffected by adenosine deaminase. Basal and insulin-stimulated glucose oxidation were little affected by adenosine deaminase. However, the addition of adenosine deaminase to fat cells incubated with 1.5 muM norepinephrine abolished the antilipolytic action of insulin and markedly reduced the increase in glucose oxidation due to insulin. These effects were reversed by N6-(phenylisopropyl)adenosine. Phenylisopropyl adenosine did not affect insulin action during a 1-hour incubation. If fat cells were incubated for 2 hours with phenylisopropyl adenosine prior to the addition of insulin for 1 hour there was a marked potentiation of insulin action. The potentiation of insulin action by prior incubation with phenylisopropyl adenosine was not unique as prostaglandin E1, and nicotinic acid had similar effects.
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PMID:Effects of adenosine deaminase on cyclic adenosine monophosphate accumulation, lipolysis, and glucose metabolism of fat cells. 16 37

Rat fat cells incubated with lipolytic agents released substances to the medium which acted as feedback regulators of cyclic adenosine 3':5'-monophosphate (cyclic AMP) accumulation. The feedback regulators were not removed by adenosine deaminase. Dialyzed medium that had previously been incubated with fat cells in the presence of norepinephrine markedly inhibited cyclic AMP accumulation by fresh cells, whereas dialyzed medium from control cells did not inhibit cyclic AMP accumulation. The effects of lipolytic agents could be mimicked by adding dialyzed medium previously incubated with fat cells in the presence of oleic acid. This suggested that free fatty acids were the nondialyzable and adenosine deaminase-insensitive inhibitors of cyclic AMP accumulation released to the medium by fat cells incubated with lipolytic agents. The regulatory function of free fatty acids was related to the molar ratio of fatty acid to albumin. Profound inhibition of both lipolysis and cyclic AMP accumulation was seen as the free fatty acid/albumin ratio exceeded 3. The inhibition of cyclic AMP accumulation by oleate was seen as soon as there was a detectable increase in cyclic AMP due to lipolytic agents. Protein kinase activity (in the presence of cyclic AMP) of the infranatant obtained after centrifugation of fat cell homogenates at 48,000 x g was inhibited by medium from cells incubated with lipolytic agents or added oleate. Adenylate cyclase activity of rat fat cell ghosts was also inhibited by dialyzed or nondialyzed medium that previously had been incubated with lipolytic agents or added fatty acids. The direct addition of oleate markedly inhibited adenylate cyclase activity as the free fatty acid/albumin ratio exceeded 2. These data suggest that the prolonged drop in cyclic AMP accumulation seen during the incubation of rat fat cells with lipolytic agents is due to the inhibition of adenylate cyclase. This occurs when the free fatty acid/albumin ratio exceeds 3.
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PMID:Free fatty acids as feedback regulators of adenylate cyclase and cyclic 3':5'-AMP accumulation in rat fat cells. 16 52

Protein kinase, phosphodiesterase and adenylate cyclase of plasma membrane of adipocytes and the effect of the feedback regulator (FR) on these three enzymes was measured and compared. The basal level ratio of adenylate cyclase to phosphodiesterase to protein kinase was 1:1.9:3.0. Epinephrine and/or FR alters this ratio. FR stimulated protein kinase activity up to 3 fold in the presence of a wide range of enzyme concentrations, 5-50 mug membrane protein/tube. The concentration of FR effective for stimulation of membrane protein kinase was much greater than that needed for inhibition of adenylate cyclase and phosphodiesterases. The inhibition by FR on adenylate cyclase was the most potent effect among the 3 enzymes. 1 U (or 2 U/ml) of FR inhibited 50% of the adenylate cyclase activity in a defined system. The maximum effective concentration of FR for stimulation of membrane protein kinase was greater than 10 U/ml. Histone type 11A was the best substrate for protein phosphorylation so far observed. The FR stimulatory effect was observed at all substrate concentrations used ranging from 1-5 mg/ml. A NaF concentration curve shows that 15 mM NaF gave maximum phosphorylation. The stimulatory effect of FR was observed both in the presence and absence of NaF. Protein kinase of adipocyte plasma membrane was mainly cAMP-independent. The effect of FR (20 U/ml) in stimulation of protein phosphorylation was much greater than that of cAMP (1 X 10(-6) M). The cAMP and FR effects seemed to be additive. Preincubation of plasma membrane with FR in the absence of ATP resulted in no decrease but slight increase in protein kinase activity. A shift in protein kinase, phosphodiesterase and adenylate cyclase ratios by FR suggests the regulatory role of FR in cAMP metabolism in adipocytes.
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PMID:Influence on adipocyte plasma membrane bound protein kinase by feedback regulator. 17 96

There is evidence than adenosine 3',5'-monophosphate (cAMP) and guanosine 3',5'-monophosphate (cGMP) may have antagonistic actions on cell growth, with cAMP inhibiting and cGMP stimulating this process. However, reductions in cAMP and increases in cGMP are not charactersitic of all neoplastic tissues. Thus, benign and malignant tissues from hepatoma-bearing rats exposed to the hepatic carcinogen DL-ethionine have elevated rather than depressed cAMP, compared to control liver, and parenteral administration of this drug increases hepatic cAMP within hours. In the present study, the effects of ethionine ingestion on the hepatic content and metabolism of both cAMP and cGMP were examined sequentially in rats at 2 and then 6 wk intervals, from the initiation of drug administration until the development of hepatomas. After 2 wk, cAMP content of quick-frozen liver from rats receiving ethionine (E) was significantly increased (826 +/- 91 pmole/g wet weight) above that of liver from pair-fed controls (C, 415 +/- 44), whether calculated by tissue wet weight, protein, or DNA content. In benign tissue from E, higher cAMP was still evident after in vitro incubations of slices with 2 mM 1-methyl-3-iso-butylxanthine (MIX) and was associated with enhanced adenylate cyclase and unchanged high or low Km cAMP-phosphodiesterase activities. These findings are compatible with accelerated cAMP generation in liver from E. Protein kinase activity ratios were significantly increased in frozen liver from E (0.52 +/- 0.04 versus 0.36 +/- 0.03 in C), and the percent glycogen synthetase in the I form was clearly reduced (19% +/- 2% in E versus 47% +/- 5% in c). incubation of hepatic slices from E or C with MIX and/or 10 muM glucagon further increased cAMP and protein kinase activity ratios, data which imply higher effective, as well as total, cellular cAMP in E. Changes in cAMP metabolism and action observed at 2 wk persisted throughout the 38-wk period of drug ingestion. Adenylate cyclase activity, cAMP content, and protein kinase activity ratios of ethionine-induced hepatomas exceeded those of both the surrounding liver from tumor-bearing rats and that of control liver, but alterations in these parameters were qualitatively similar in both tissues from E. By contrast, while cGMP in quick-frozen surrounding liver from tumor-bearing rats (36 +/- 4 pmole/g wet weight) did not differ from that of control liver (30 +/- 3), cGMP in the hepatomas was increased. This change was evident in both frozen tumor (89 +/- 10) and in tumor slices incubated in vitro with MIX (C, 90 +/- 11; surrounding liver, 85 +/- 10; hepatoma 231 +/- 29). These results indicate that malignant conversion can occur in liver with a sustained elevation of both total and effective cAMP during the premalignant phase. The increase in cGMP detected in ethionine-induced hepatomas could also be a key determinant of malignant transformation in the model, although premalignant changes in cGMP were not apparent.
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PMID:Sequential alterations in the hepatic content and metabolism of cyclic AMP and cyclic GMP induced by DL-ethionine: evidence for malignant transformation of liver with a sustained increase in cyclic AMP. 18 92

Fat cell ghosts and homogenates of fat cells were used to study the influence of training on the regulatory system for lipolysis in adipose tissue of female rats. A training effect was identified from elevated succinate dehydrogenase activities in the soleus and plantaris muscles. Neither basal nor maximal (NaF-stimulated) adenylate cyclase activities per mg protein of fat cell ghosts were altered by training. Fluoride-stimulated adenylate cyclase activity per microgram DNA was lower in the trained than untrained group. Adenylate cyclase activities in response to norepinephrine expressed either on a per mg protein or per microgram DNA basis were lower (P less than 0.05) in fat cell ghosts from trained rats. Phosphodiesterase activity was higher (P less than 0.05) in fat cell ghosts from trained rats for cyclic AMP concentrations of 1--5.0 micrometer. The apparent Km's of phosphodiesterase were 1.19 and 2.0 micrometer of cyclic AMP for the untrained and trained groups, respectively (P less than 0.05). Protein kinase activity in the supernatant fraction of homogenates of fat cells was unchanged due to training. The overall effect of training was to blunt the system for cyclic AMP production in rat adipocytes. This may explain, at least partially, the lower plasma free fatty acid levels observed in trained compared to untrained persons during submaximal exercise.
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PMID:Effect of physical training on control mechanisms of lipolysis in rat fat cell ghosts. 19 25

Protein kinase that phosphorylated histone and lesser amounts of protamine was demonstrated in human heart. It was activated three times by 10(-6) M cyclic adenosine 3':5'-monophosphate (cAMP) and by 10(-3) M other cyclic nucleotides. Km values for cAMP, ATP, Mg2+, and Co2+ were about 2 X 10(-8) M, 4 X 10(-5) M, 2 X 10(-3)M, and 1.7 X 10(-4) M, respectively. On DEAE cellulose column, the main peak of the enzyme eluted at high NaCl concentration. On Sephadex G-200 gel filtration the majority of the holoenzyme eluted at a peak corresponding to a molecular weight of about 300,000. There was an additional peak corresponding to a molecular weight of about 400,000, with relatively high cAMP binding compared to kinase activity. Right atrium and ventricle showed significantly higher enzyme activities than left atrium and ventricle and interventricular septum. On multivariate analysis of the enzyme activity versus 12 clinical and pathological findings of 122 cases, cardiac hypertrophy and coronary sclerosis were slight but significant negative contributors to the enzyme activity. Multiple correlation coefficient was low, indicating the enzyme activity remained at a relatively stable level, despite different clinical situations. This may be suitable for control of intracellular events through the membrane adenylate cyclase system.
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PMID:An adenosine 3':5'-monophosphate-dependent protein kinase from human heart. 20 85

cAMP-dependent protein kinase activity was present in a soluble TSH 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 cAMP. A [3H]cAMP-binding protein was also found in this fraction. The Ka for [3H]cAMP-binding was 0.11 X 10(6) M-1, with a total binding capacity of 3 nmol/mg protein. After fractionation using a continuous sucrose density gradient, one of the several [125I]iodobovine TSH-binding peaks corresponded to a [3H]cAMP-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 shown. This protein kinase activity was stimulated by adding 10(-5) M cAMP. A peak of [3H]cAMP-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 has an adenylate cyclase activity stimulated by TSH. These results suggest that some TSH receptors released from thyroid plasma membranes have associated adenylate cyclase activity and cAMP-dependent protein kinase activity. The receptor, cyclase, and kinase activities may exist in a functional primary receptor unit which is spontaneously released from plasma membranes.
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PMID:Adenosine 3',5'-monophosphate-dependent protein kinase activity in soluble thyrotropin receptor complex. 22 Nov 90

Two subfractions of bovine thyroid plasma membranes, light membranes (L-membranes) and heavy membranes (H-membranes), were obtained by a discontinuous sucrose gradient centrifugation of plasma membranes. Electron microscopy of the plasma membrane and its subfractions showed that the H-membranes were very similar to the plasma membrane fraction, both contained junctional complexes, long membrane sheets, and vesicles. In contrast, the L-membranes consisted mainly of short membrane sheets and vesicles, and only a few junctional complexes. The H-membranes had greater adenylate cyclase activity which responded to thyroid-stimulating hormone (TSH) while this hormone had very little effect on the enzyme activity in the L-membranes. Despite the marked difference in TSH stimulation of adenylate cyclase activity in the H- and L-membrane fractions, specific binding of 125I-TSH was similar in both fractions. The L-membranes had higher specific activities of 5'-nucleotidase and Mg2+ATPase while (Na+ + K+)-ATPase and alkaline phosphatase activities were similar in the two subfractions. Protein kinase activity of H-membranes was not significantly stimulated by exogenous cyclic adenosine 3':5'-monophosphate (cAMP). Plasma membranes and H-membranes contained a substrate capable of being phosphorylated. Such phosphorylation was slightly increased by addition of soluble protein kinase. The phosphorylation of exogenous histone by protein kinase of plasma membranes and H-membranes was augmented by cAMP. In contrast, L-membranes had very little protein kinase activity even when exogenous histone was added. They were not a very good substrate for cytosolic protein kinase.
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PMID:Preparation and characterization of subfractions of bovine thyroid plasma membranes. 85 12

Regulation of prostaglandin (PG) E2 receptors was investigated in a 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate-solubilized fraction from the synaptic membrane of porcine temporal cortex. The fraction was preincubated with exogenous protein kinases, and then the binding of PGE2 was measured. PGE2 binding was increased approximately twofold by pretreatment with the catalytic subunit of cyclic AMP-dependent protein kinase (A kinase) or calmodulin-dependent protein kinase II but not by that with protein kinase C. The increase was dependent on the ATP concentration, with ED50 values being close to the Km values of these protein kinases. Protein kinase inhibitors specific for A kinase and for calmodulin-dependent protein kinase II abolished the effect in a dose-dependent manner, with IC50 values being similar to those reported. Further study using the catalytic subunit of A kinase revealed that the maximal binding capacity apparently increased without affecting the affinity and the rate constants for association and dissociation. On the other hand, acid phosphatase treatment reduced the binding activity to the level of nonspecific binding. In addition, treatment by A kinase did not affect the binding of guanosine 5'-(3-thiotriphosphate) by the GTP-binding proteins and the activation of adenylate cyclase mediated by stimulatory guanine nucleotide-binding regulatory protein, and therefore the phosphorylation is believed to occur on the receptor protein. The results suggest that the PGE2 receptor can take active phosphorylated and inactive dephosphorylated forms, of which only the phosphorylated one can bind PGE2.
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PMID:Regulation of prostaglandin E2 receptor binding activity in porcine temporal cortex by protein phosphorylation. 165 90


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