scholarly journals Factors affecting the activity of guanylate cyclase in lysates of human blood platelets

1978 ◽  
Vol 174 (1) ◽  
pp. 23-35 ◽  
Author(s):  
A F Adams ◽  
R J Haslam
Keyword(s):  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Specific Activity ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Cyclase Activity ◽  
Temperature Dependent ◽  
Factors Affecting ◽  
Guanylate Cyclase Activity ◽  
Triton X

1. Under optimal ionic conditions (4 mM-MnCl2) the specific activity of guanylate cyclase in fresh platelet lysates was about 10nmol of cyclic GMP formed/20 min per mg of protein at 30 degrees C. Activity was 15% of optimum with 10mM-MgCl2 and negligible with 4mM-CaCl2. Synergism between MnCl2 and MgCl2 or CaCl2 was observed when [MnCl2] less than or equal to [GPT]. 2. Lower than optimal specific activities were obtained in assays containing large volumes of platelet lysate, owing to the presence of inhibitory factors that could be removed by ultrafiltration. Adenine nucleotides accounted for less than 50% of the inhibitory activity. 3. Preincubation of lysate for 1 h at 30 degrees C increased the specific activity of platelet guanylate cyclase by about 2-fold. 4. Lubrol PX (1%, w/v) stimulated guanylate cyclase activity by 3–5-fold before preincubation and by about 2-fold after preincubation. Triton X-100 was much less effective. 5. Dithiothreitol inhibited the guanylate cyclase activity of untreated, preincubated and Lubrol PX-treated lysates and prevented activation by preincubation provided that it was added beforehand. 6. Oleate stimulated guanylate cyclase activity 3–4-fold and arachidonate 2–3-fold, whereas palmitate was almost inactive. Pretreatment of lysate with indomethacin did not inhibit this effect of arachidonate. Oleate and arachidonate caused marked stimulation of guanylate cyclase in preincubated lysate, but inhibited the enzyme in Lubrol PX-treated lysate. 7. NaN3 (10mM) increased guanylate cyclase activity by up to 7-fold; this effect was both time- and temperature-dependent. NaN3 did not further activate the enzyme in Lubrol PX-treated lysate. 8. The results indicated that preincubation, Lubrol PX, fatty acids and NaN3 activated platelet guanylate cyclase by different mechanisms. 9. Platelet particulate fractions contained no guanylate cyclase activity detectable in the presence or absence of Lubrol PX that could not be accounted for by contaminating soluble enzyme, suggesting that physiological aggregating agents may increase cyclic GMP in intact platelets through the effects of intermediary factors. The activated and inhibited states of the enzyme described in the present paper may be relevant to the actions of these factors.

scholarly journals The metabolism of cyclic nucleotides in the guinea-pig pancreas. Adenylate cyclase and guanylate cyclase

1980 ◽  
Vol 186 (2) ◽  
pp. 499-505 ◽  
Author(s):  
M Lemon ◽  
P Methven ◽  
K Bhoola
Keyword(s):  
Adenylate Cyclase ◽  
Guinea Pig ◽  
Guanylate Cyclase ◽  
Cyclic Nucleotides ◽  
Cyclase Activity ◽  
Dependent Manner ◽  
Guanylate Cyclase Activity ◽  
Triton X ◽  
Dose Dependent ◽  
Significant Activation

Adenylate cyclase from the guinea-pig pancreas was activated in a dose-dependent manner by both secretin and cholecystokinin-pancreozymin, but in contrast with results in other species the hormones were approximately equipotent. All other hormones and transmitter substances tested were without any effect on adenylate cyclase activity. Guanylate cyclase activity was shown to have both particulate and supernatant components in the guinea-pig pancreas. The particulate enzyme, but not the supernatant enzyme, was markedly activated by Triton X-100, and most of the induced activity was released into the supernatant. The supernatant enzyme was specifically Mn2+-dependent, but, even though Mn2+ was maximally effective at a concentration of 3 mM, activity could be raised further by increasing Ca2+ concentration. The particulate enzyme, by contrast, was relatively Mn2+-independent. Activity of the particulate guanylate cyclase was enhanced by phosphatidylserine. The supernatant enzyme displayed classical Michaelis-Menten kinetics, but the particulate enzyme deviated markedly from such kinetics. Under none of the conditions used was any significant activation of guanylate cyclase observed with any of the secretogen hormones or transmitter substances.

Ovarian cyclic GMP concentration and guanylate cyclase activity in immature rats after treatment with pregnant mare serum gonadotrophin

1985 ◽  
Vol 107 (1) ◽  
pp. 77-81 ◽  
Author(s):  
V. V. Patwardhan ◽  
A. Lanthier
Keyword(s):  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Particulate Fraction ◽  
Cyclase Activity ◽  
Immature Rat ◽  
Ovarian Weight ◽  
Guanylate Cyclase Activity ◽  
Immature Rats ◽  
Pregnant Mare Serum Gonadotrophin ◽  
Treatment Activity

ABSTRACT We have previously reported that the LH-induced decrease in the concentration of ovarian cyclic GMP (cGMP) in the rabbit was accompanied by a drop in ovarian guanylate cyclase activity. The present experiments were carried out to see if the increase in cGMP concentration that occurs in immature rat ovaries after stimulation with pregnant mare serum gonadotrophin (PMSG) is also accompanied by changes in guanylate cyclase activity. Total ovarian cGMP, along with ovarian weight, was found to be increased at 16 h after PMSG treatment. Ovarian concentrations of cGMP, however, increased only after that period (at 20, 24 and 48 h) and the increase was progressive. Guanylate cyclase activity was found in both the cytosol and 100 000 g particulate fractions of the immature rat ovaries. Forty-three hours after PMSG treatment, activity in the particulate fraction was found to be significantly increased. This increase in guanylate cyclase activity was also found at 20 h but not at 16 h. Thus, the increase in ovarian cGMP concentration in immature rats after PMSG treatment was accompanied by increased guanylate cyclase activity. J. Endocr. (1985) 107, 77–81

scholarly journals Guanylate cyclase activity and cyclic nucleotide concentrations during liver regeneration after experimental injury

1977 ◽  
Vol 164 (1) ◽  
pp. 33-39 ◽  
Author(s):  
Christo Goridis ◽  
Jean Zwiller ◽  
Werner Reutter
Keyword(s):  
Dna Synthesis ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Cyclic Nucleotide ◽  
Cyclase Activity ◽  
Tissue Concentrations ◽  
Guanylate Cyclase Activity ◽  
Time Period ◽  
Membrane Bound ◽  
Experimental Injury

Cyclic nucleotide concentrations and guanylate cyclase activity were measured in regenerating rat liver. Previous work has shown that in livers of partially hepatectomized rats the activity of a membrane-bound guanylate cyclase increases considerably during the early replicative phase [Kimura & Murad (1975) Proc. Natl. Acad. Sci. U.S.A.72, 1965–1969; Goridis & Reutter (1975) Nature (London) 257, 698–700]. Over the same time period after partial hepatectomy, increased tissue concentrations of cyclic GMP were found when the rats were killed under pentobarbital anaesthesia, but not when anaesthesia was omitted. The results obtained on hepatectomized livers were compared with the changes in guanylate cyclase activity and cyclic nucleotide concentrations during the response to galactosamine treatment. Here, a peak of guanylate cyclase activity and of cyclic GMP concentrations occurred at 8h, that is before the beginning of the proliferative response. Both parameters were normal at the time of increased DNA synthesis. There does not, therefore, seem to be a consistent correlation between changes in guanylate cyclase activity or concentrations of cyclic GMP and an increase in liver DNA synthesis. A modest rise in cyclic AMP concentrations was found, however, in livers of galactosamine-treated rats, which was coincident with the time of DNA synthesis.

Cyclic GMP phosphodiesterase and guanylate cyclase activities in rabbit ovaries and the effect of in-vivo stimulation with LH

1984 ◽  
Vol 101 (3) ◽  
pp. 305-310 ◽  
Author(s):  
V. V. Patwardhan ◽  
A. Lanthier
Keyword(s):  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
The Other ◽  
Particulate Fraction ◽  
Cyclase Activity ◽  
Supernatant Fraction ◽  
Phosphodiesterase Activity ◽  
Significant Drop ◽  
Guanylate Cyclase Activity

ABSTRACT The activities of guanylate cyclase and cyclic GMP (cGMP) phosphodiesterase, enzymes that are responsible for maintaining tissue levels of cGMP, were determined in the ovaries of rabbits killed without treatment or 4 h after administration of LH. Ovarian activities of the two enzymes were determined in the 100 000 g supernatant fraction (cytosol) and the resulting pellet (particulate fraction). Significant phosphodiesterase and cyclase activities were detected in both the cytosol and particulate fractions. Administration of LH had no significant effect on phosphodiesterase activity in either of the tissue fractions. On the other hand, LH caused a significant drop in guanylate cyclase activity in the cytosol and particulate fractions. This drop in the cyclase activity may be the cause of the decreased rabbit ovarian concentrations of cGMP that we have previously observed after LH stimulation. J. Endocr. (1984) 101, 305–310

scholarly journals Regulation of guanylate cyclase in guinea-pig islets of Langerhans

1974 ◽  
Vol 142 (2) ◽  
pp. 379-384 ◽  
Author(s):  
Simon L. Howell ◽  
William Montague
Keyword(s):  
Guinea Pig ◽  
Islets Of Langerhans ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Phosphodiesterase Inhibitor ◽  
Cyclase Activity ◽  
Insulin Biosynthesis ◽  
Ph Optimum ◽  
Neutral Alumina ◽  
Guanylate Cyclase Activity

1. Guanylate cyclase activity was determined in homogenates of guinea-pig islets of Langerhans by measurement of the conversion of [α-32P]GTP into cyclic [32P]GMP, the reaction products being separated on columns of neutral alumina. 2. The pH optimum of the enzyme was 7.3; it showed a requirement for bivalent cations, the effectiveness of the cations tested being Mn2+»Ca2+>Mg2+. 3. About 70% of enzyme activity was sedimented by centrifugation at 105000g for 60min; activity was increased 2.3-fold by treatment of homogenates with 0.1% Triton X-100. 4. Guanylate cyclase activity of homogenates was increased by acetylcholine, secretin or pancreozymin, but was inhibited by adrenaline, noradrenaline or ATP. Insulin, glucagon, prostaglandins E1 or E2, glucose, F-, diazoxide or glibenclamide were ineffective. 5. Determination of cyclic GMP amounts in islets by radioimmunoassay showed a basal concentration of 2.0pmol/mg of protein, which was increased by incubation of the islets in the presence of acetylcholine or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, but was unaffected by glucose. 6. Dibutyryl cyclic GMP had significant stimulatory effects on rates of insulin biosynthesis in isolated rat islets of Langerhans. 7. These results suggest a possible role for cyclic GMP in the regulation of insulin biosynthesis and secretion.

scholarly journals The Phytosulfokine (PSK) Receptor Is Capable of Guanylate Cyclase Activity and Enabling Cyclic GMP-dependent Signaling in Plants

2011 ◽  
Vol 286 (25) ◽  
pp. 22580-22588 ◽  
Author(s):  
Lusisizwe Kwezi ◽  
Oziniel Ruzvidzo ◽  
Janet I. Wheeler ◽  
Kershini Govender ◽  
Sylvana Iacuone ◽  
...  
Keyword(s):  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Cyclase Activity ◽  
Guanylate Cyclase Activity
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