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)

Incubation of raty erythrocytes and reticulocytes in Tris-Ringer's medium with 5 mM cyclic-AMP or AMP increased lactate formation and glucose utilization. The glycolysis-stimulating effect of cyclic-AMP is very similar to that of AMP and, in both cases, it seems to be higher in reticulocytes than in erythrocytes. 0.5 mM norepinephrine produced a much higher lactate formation in reticulocytes than in erythrocytes, suggesting a greater adenylate cyclase activity in younger cells. 300 micrometer cyclic-AMP and AMP reverse inhibition produced by ATP (up to 1.5 micrometer) on phosphofructokinase from rat reticulocyte haemolysates. Both nucleotides are positive allosteric effectors of the enzyme as shown by displacement of F6P-saturation curve to hyperbolic kinetics. Similar results were previously obtained with rat erythrocytes. This deinhibitory effect is suggested to be responsible of the above glycolysis-stimulating effect.
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PMID:Comparative activation by AMP and cyclic-AMP of rat erythrocyte and reticulocyte glycolysis. 20 50

In the fully grown Bufo arenarum oocyte, carbohydrate breakdown during the autumn-winter season is accomplished mainly through the glycolytic pathway followed by the Krebs cycle. During the breeding season (spring-summer), carbohydrates are used mainly through the pentose phosphate cycle and through the variant of the Krebs cycle known as the glutamic aspartic cycle. The metabolism operating in the oocytes was determined using the following parameters: 1) the capacity of isolated mitochondria to oxidize citrate and fumarate; 2) the enzymatic activities of phosphofructokinase (PFK) and glucose-6-phosphate dehydrogenase (G-6-PDH); and 3) citrate and ATP compartmentalization. The present paper shows that follicle-stimulating hormone (FSH) would be one of the factors responsible for summer metabolism, since ovary fractions obtained from winter specimens treated with the hormone acquired the metabolic characteristics corresponding to oocytes obtained from breeding-season animals. From dose-response, and response in the function of time curves, it could be assumed that the optimum doses and times were 0.1 micrograms FSH/ml of incubation medium and 30 min treatment, respectively. The metabolic effect of FSH upon oocytes could be mediated by the adenylate cyclase-cAMP system, since treatment of ovaric fractions with cAMP 10(-3) M reproduced the effects obtained with the hormone. In addition, 0.02 mg/ml tetracycline proved to block the effect of FSH. A direct metabolic action of FSH on body cavity oocytes (without follicle cells) was observed when submitting these oocytes to the same hormonal treatment.
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PMID:Effect of follicle-stimulating hormone on metabolism and maturation in Bufo arenarum oocytes. 250 14

Mg2+-ATPase activity was identified in the cytosol of human erythrocytes. A partial purification of this activity was achieved by an initial DEAE-Sephadex column chromatography, followed by gel filtration on Sephadex G-100 and then a second DEAE-Sephadex chromatography procedure. The enzyme appeared in the void volume of the Sephadex G-100 column and was retained on an Amicon XM100A ultrafiltration membrane. The molecular weight of the enzyme was estimated to be 113 000 from SD gels. The above purification protocol yielded an enzyme with an optimal pH between 7.6 and 8.2. The enzyme activity increased linearly between 30 and 44 degrees C. It was stable for several months at -20 degrees C. Magnesium was essential for activity, but the rate attainable with Mn2+ was at least as great as that due to Mg2+. No other divalent cation was able to substitute for Mg2+ or Mn2+. Neither low nor high Ca2+ concentrations significantly affected the enzymatic activity. Substrate specificity studies showed that ATP was the preferred substrate followed by CTP (46% of the rate produced by ATP). Hydrolysis of GTP, UTP, ITP and ADP was less than 10% of the rate seen with ATP. No phosphatase, pyrophosphatase, phosphodiesterase, hexokinase, phosphofructokinase or adenylate cyclase activity could be detected in this enzyme preparation. Calmodulin, which stimulates the (Ca2+ + Mg2+)-ATPase of the human erythrocyte membrane, failed to enhance the Mg2+-ATPase activity. Of considerable interest, the activity of this Mg2+-ATPase was enhanced approximately 5-fold by low concentrations of mercuric ion, p-hydroxymercuribenzoate and DTNB, but was much less sensitive to iodoacetamide.
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PMID:Partial purification and characterization of a novel Mg2+-dependent ATPase present in the cytosol from human erythrocytes. 615 Jul 30

It is evident from the above review that during the last two decades a great deal of interest in investigating the action of serotonin in parasitic worms has been shown by parasitologists as well as by scientists from several other disciplines. What we have initially reported concerning the effect of serotonin on motility and carbohydrate metabolism of F. hepatica has been pursued on several other parasitic worms. The studies so far indicate that serotonin stimulates motility of every species tested among the phylum Platyhelminthes. The indoleamine also stimulates glycogenolysis in the few flatworm parasites that have been investigated. The information in nematodes is scanty and the role of serotonin in these parasites is still open for experimentation. Recent biochemical investigations on F. hepatica and S. mansoni demonstrated that serotonin and related compounds utilize a common class of receptors in plasma membrane particles which I designate as 'serotonin receptors'. These receptors are linked to an adenylate cyclase that catalyses the synthesis of the second messenger, cyclic 3',5'-AMP. Serotonin and its congeners increase the concentration of cyclic AMP in intact parasites whereas antagonists inhibit such an effect. Cyclic AMP stimulates glycogenolysis, glycolysis and some rate-limiting glycolytic enzymes. It activates a protein kinase that may be involved in activation of glycogen phosphorylase and phosphofructokinase. Serotonin-activated adenylate cyclase in S. mansoni is activated early in the life of the schistosomule. The possibility is discussed that the availability of cyclic AMP through serotonin activation in these parasites may be a prelude to the development processes that take place in the parasite. The different components of the serotonin-activated adenylate cyclase in the parasite are the same as those that have been previously described for the host. Binding characteristics of the receptors indicate that the receptors in F. hepatica appear to be different from those that have been described in the host. The discovery of these receptors and their differences from those in the host offer a new site which is amenable to pharmacological manipulation. The search for new agents that influence serotonin receptors in these parasites could be included in a strategy for the development of new chemotherapeutic agents against these parasites.
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PMID:Serotonin receptors in parasitic worms. 615 76

In human red blood cell there is complete adenyl cyclase--cAMP system. However, the role of this system and its connection with energy metabolism in red cell is not known. Hence, we studied the effects of cAMP and DB-cAMP on energy metabolism in human red cell. Blood was taken out from haematologically healthy volunteers. Red cells were isolated by differential centrifugation and washed three times in Tris-Ringer buffer (pH 7.4). The red cells suspensions (in the above buffer) were simultaneously incubated without additions (control) and with cAMP or DB-cAMP (5 mmol/L). Incubation temperature was 37 degrees C. The samples of suspensions for the extraction of metabolites and cofactors were taken at 0 and 180 minutes of incubation. The lactate, glucose, G6P, F6P, TP, ATP, ADP and AMP were determined in neutralized perchloric acid extracts by specific enzymatic methods. Results of our experiments show that cAMP and DB-cAMP significantly increase red cell glycolysis. Under the same conditions these nucleotides induce positive "cros-over" point at the phosphofructokinase (PFK) step of the glycolysis. The levels of adenine nucleotides (ATP, ADP, AMP) were unchanged through a whole period of incubation. We concluded that cAMP and DB-cAMP stimulates glycolytic process in red cells probably by allosteric activation of PFK.
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PMID:[The role of cAMP in the energy metabolism of human erythrocytes]. 629 68

Under certain growth conditions, some strains of Escherichia coli accumulate toxic levels of methylglyoxal. This report characterizes a strain which synthesizes a mutant cAMP receptor protein in an adenylate cyclase deletion background. When cultured in glucose 6-phosphate minimal medium, this strain (222) was prematurely growth arrested due to methylglyoxal production; growth inhibition did not occur when the strain was grown in glucose minimal medium. A comparison of a variety of enzyme and cofactor levels in the related strains 222 (mutant) and 225 (wild-type) grown on either glucose or glucose 6-phosphate medium was carried out. The only difference found that might explain an increase in methylglyoxal accumulation was an elevated level of phosphofructokinase in strain 222 grown on glucose 6-phosphate. Since this enzyme activity probably limits hexose phosphate metabolism, it is suggested that growth inhibition in strain 222 may be due to increased production of triose phosphate, some of which is converted to methylglyoxal.
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PMID:Methylglyoxal-mediated growth inhibition in an Escherichia coli cAMP receptor protein mutant. 630 83

The patterns of temporal self-organization in regulated biochemical systems are examined. Simple periodic oscillations are the most frequent type of such organization, as exemplified by glycolytic oscillations in yeast and muscle and by the periodic synthesis of adenosine 3',5'-cyclic monophosphate in Dictyostelium discoideum amoebas. These phenomena originate, respectively, from the periodic operation of the product-activated phosphofructokinase and adenylate cyclase reactions. The analysis of a model for a multiply regulated biochemical system shows more complex oscillatory phenomena, e.g., the coexistence between two stable periodic regimes for the same set of parameter values (birhythmicity) and chaos. The latter phenomenon of aperiodic oscillations occurs in a narrow range of parameter values and is much less frequent than simple or complex periodic behavior. It is suggested that a sufficient condition for the occurrence of birhythmicity and chaos in a regulated biological system subjected to a constant environment (i.e., in the absence of periodic forcing) may be the simultaneous presence and interaction of two mechanisms capable of producing oscillations.
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PMID:Temporal self-organization in biochemical systems: periodic behavior vs. chaos. 631 16

A number of soluble and membrane associated enzymes of glycolysis, pentose phosphate pathway and other related enzymes were measured in three different brain regions during aging. Enzymes utilizing and synthesizing peroxides were also included. Increasing levels of peroxidative products are known to accumulate in the brain with age. The membrane associated enzymes were found to be the primary focus of damage. Phosphofructokinase and glucose-6-phosphate dehydrogenase exhibited an unusual pattern when measured in whole homogenates. A progressive decrease in the synaptosomal bound hexokinase was found with increasing age. The synaptosomal phosphofructokinase (PFK) also showed a significant decrease with aging. Significant decrease in the incorporation of myoinositol into phospholipids and a loss of activity of membrane bound adenylate cyclase with age indicated that changes must be occurring in the structure of the brain and the loss of cerebral competence in the senescent brain may arise from peroxidative damage to membranes.
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PMID:Effect of aging on soluble and membrane bound enzymes in rat brain. 2050 79