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)

Various studies have shown that the lipolytic response of white adipocytes to catecholamines was dependent on the anatomical origin of these cells. To provide a biological explanation for this phenomenon, we compared hamster white adipocytes, from femoral subcutaneous and epididymal fat, for their lipolytic activities, cAMP responses and adrenoceptor-coupled adenylate cyclase system. Basal and maximal lipolytic responses to the beta-adrenergic (isoproterenol) and the mixed alpha 2/beta-adrenergic (epinephrine) agonists were lower in femoral subcutaneous cells than in epididymal cells, but the alpha 2-adrenergic antilipolytic response to 5-bromo-6-(2-imidazolin-2-ylamino)quinoxaline bi-tartate (UK14304) was slightly greater in femoral subcutaneous fat cells than in epididymal fat cells. Identical results were observed for cAMP responses, except for the alpha 2-adrenergic inhibitory response which was identical in both fat deposits. Adrenoceptors studies revealed higher density of inhibitory alpha 2-adrenoceptors 2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline ([3H]RX821002-binding sites) in femoral subcutaneous fat cells than in epididymal fat cells, but identical density of stimulatory beta-adrenoceptors (125I-cyanopindolol-binding sites) and similar subdivision into beta-adrenoceptor subtypes in both adipose deposits. Finally, the level of the alpha-subunits of the stimulatory and inhibitors guanine-nucleotide-binding regulatory proteins, as well as the adenylate cyclase catalytic activity were 40-50% lower in femoral subcutaneous fat cell membranes than in epididymal fat cell membranes. These results suggest that the differences in cAMP and lipolytic responses to catecholamines between epididymal and femoral subcutaneous adipocytes result at least in part from site-related differences in the adenylate cyclase system rather than in the adrenoceptor status.
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PMID:Characteristics of the alpha 2/beta-adrenoceptor-coupled adenylate cyclase system and their relationship with adrenergic responsiveness in hamster fat cells from different anatomical sites. 134 84

1. Short-circuit current (SCC) technique was used to study the adrenoceptors involved in the electrogenic chloride secretion by cultured cauda epididymal epithelium of rats. Stimulation of the epithelium with noradrenaline (primarily beta 1-adrenoceptor selective agonist), salbutamol (beta 2-adrenoceptor selective agonist) and adrenaline (non-selective beta-adrenoceptor agonist) led to a rise in SCC. At a low chart-speed (2 mm min-1), the response profile to these agonists consisted of a peak followed by a sustained response considerably higher than the basal SCC. 2. The EC50s (doses of agonist producing 50% maximum response) of noradrenaline, salbutamol and adrenaline were 300, 115 and 10 nM respectively. Pretreating the tissues with 1 microM atenolol (beta 1-selective antagonist) and 10 microM butoxamine (beta 2-selective antagonist) shifted the dose-response curves of noradrenaline (shifted EC50 = 4000 nM) and salbutamol (shifted EC50 = 1050 nM) to the right. Atenolol (1 microM) and butoxamine (10 microM) shifted the dose-response curve of adrenaline to the right with new EC50s of 30 nM and 115 nM, respectively. 3. The rapidly rising phase of the SCC response to noradrenaline and adrenaline observed at low chart-speed consisted of a brief and transient retraction followed by a rebound increase in SCC. At a high chart-speed (1 mm s-1), the retraction and rebound phenomenon manifested as a fast initial spike which could be blocked by phentolamine (non-specific alpha-adrenoceptor antagonist) in a dose-dependent fashion. Similar initial spikes were observed when the tissues were stimulated with phenylephrine (alpha-selective agonist) but not with isoprenaline (non-selective beta-agonist) or forskolin (activator of adenylate cyclase). The response of the initial spike triggered by noradrenaline was dose-dependent and the EC50 was 2000 nM.4. The present study showed that the electrogenic chloride secretion by rat epididymis could be stimulated by (alphaxi-, beta131- and beta2-adrenoceptor agonists. The al-mediated response had a faster onset and more transient action than the 3-counterpart. It is postulated that epididymal chloride secretion might be regulated by neural (noradrenaline-mediated) and humoral (adrenaline-mediated) controls and that the stimulus-secretion coupling mechanisms might involve both Ca2+(alpha-mediated response) and adenosine 3':5'-cyclic monophosphate (beta-mediated response) as intracellular second messengers.
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PMID:Characterization of adrenoceptors involved in the electrogenic chloride secretion by cultured rat epididymal epithelium. 135 80

Anion transport inhibitors, such as SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid) and heparin, inhibit reversibly the bicarbonate-sensitive adenylylcyclase of porcine sperm plasma membrane. In the light of this, SITS- and heparin-affinity chromatographies were applied in order to purify sperm adenylylcyclase. SITS-Affi-Gel 102 binds proteins extracted from the porcine cauda epididymal sperm plasma membrane by Lubrol-PX, more selectively than heparin-agarose. However, recovery of adenylylcyclase activity is higher when heparin-agarose is used. The hormone-sensitive liver adenylylcyclase, which is less sensitive to bicarbonate than sperm enzyme, has less affinity for these affinity resins than sperm enzyme. Adenylylcyclase can be purified to apparent homogeneity on two-dimensional gel electrophoresis (isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis) from the Lubrol-PX extract of the purified sperm plasma membrane by using SITS-affinity chromatography at the first step of the purification followed by preparative isoelectric focusing and gel filtration. The molecular weight and pI of the purified enzyme are 46,300 and 6.9, respectively. The purified enzyme activity is highly dependent on Mn2+. Bicarbonate activates even the purified enzyme both by decreasing Km and by increasing Vmax.
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PMID:Purification of bicarbonate-sensitive sperm adenylylcyclase by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid-affinity chromatography. 165 24

Exposure of rat epididymal fat pad to phorbol 12-myristate 13-acetate (TPA), an activator of protein kinase C, results in an 85% increase in isoproterenol-stimulated cyclic AMP (cAMP) accumulation, an effect which was antagonized by H7, a protein kinase C inhibitor. This promoting action of TPA appears to be related to (i) an increase in the catalytic activity of adenylate cyclase, (ii) an increase in the maximal response of adenylate cyclase to fluoride and guanylimidodiphosphate (GppNHp) with no change in the EC50 value for GppNHp, and (iii) a reduction of the isoproterenol-stimulated low-Km cAMP phosphodiesterase activity present in the 30,000 g pellet of fat pad homogenates. In contrast with fat pads, exposure of isolated rat fat cells to TPA failed to influence their adenylate cyclase response to GppNHp and their cAMP accumulation and lipolysis. However, the other alterations caused by TPA in fat pads were still observed in fat cells. These results suggest that (i) the major alteration responsible for the promoted isoproterenol-stimulated cAMP response observed in fat pads after exposure to TPA is an increased interaction between the alpha s subunit of Gs and the catalytic site of adenylate cyclase and (ii) this increased interaction is dependent on protein kinase C activation and is abolished by collagenase digestion.
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PMID:Differential modulation of the adenylate cyclase/cyclic AMP stimulatory pathway by protein kinase C activation in rat adipose tissue and isolated fat cells. Influence of collagenase digestion. 165 98

We found that anion channel blockers such as phosphotungstate and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS) enhanced HCO3(-)-induced activation on porcine epididymal sperm. In the presence of these compounds, HCO3- increased the motility, respiration rate and especially the cAMP content of the sperm to a greater extent than did HCO3- alone. The enhancing effects were not observed in the absence of HCO3-, but were evident when the concentration of HCO3- was low. These compounds did not significantly alter the intracellular pH and did inhibit the adenylate cyclase activity of the sperm plasma membrane. When these compounds were added to sperm homogenate with ATP, the cAMP formed was reduced compared to the control. In addition, these compounds inhibited both the SO4(2-) influx and efflux of the sperm. From these results, we conclude that the anion channel blockers tested principally inhibit the efflux of endogenous HCO3- derived from metabolic CO2, so that HCO3- accumulates intracellularly and stimulates the adenylate cyclase of the sperm.
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PMID:The enhancing effects of anion channel blockers on sperm activation by bicarbonate. 169 90

The decrease in motility of porcine cauda epididymal sperm was less than that of caput epididymal sperm in the medium containing bicarbonate. This may be due to the difference of sensitivity of adenylate cyclase to bicarbonate between mature and immature sperm; activation of mature sperm enzyme by bicarbonate was higher than that of immature sperm. Nondialysable fraction of egg yolk prevented the decrease in motility of immature sperm in the presence of bicarbonate, but it was not effective for the motility of mature sperm under the same condition, because only bicarbonate is sufficient for the maintenance of its motility. In the absence of bicarbonate, both mature and immature sperm required egg yolk to maintain motility. The favorable effect of egg yolk on the motility is ascribed to the enhancement of intracellular cAMP level. Partial fractionation of egg yolk showed that water-insoluble lipoprotein fraction contains factor(s) which activates adenylate cyclase in sperm plasma membrane. This is the first report in which high molecular weight activator of the sperm enzyme was demonstrated.
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PMID:Water insoluble fraction of egg yolk maintains porcine sperm motility by activating adenylate cyclase. 184 69

Previous studies from this laboratory and others have identified several enzymes on the surface of mammalian spermatozoa. Some of these enzymes, namely a galactosyltransferase and a novel alpha-D-mannosidase, are believed to play a ligand-like role in recognizing and binding to the complementary moiety(ies) present on zona pellucida glycoconjugates. However, little or no information is available about the occurrence of these enzymes in human spermatozoa. In the present report, we show that a very small amount of the total galactosyltransferase activity present in human semen is associated with spermatozoa. Moreover, our failure to find a significant amount of the enzyme on sperm plasma membranes suggests that the enzyme is not associated with the sperm surface. Therefore, it is unlikely that galactosyltransferase in humans has the same ligand-like role in zona binding that is demonstrated in mouse sperm. In contrast, nearly 5% of alpha-D-mannosidase activity was repeatedly found in the salt-washed plasma membrane fraction. The recovery and enrichment of the alpha-D-mannosidase was nearly one-half that observed for adenylate cyclase and nearly one-third that for phosphodiesterase I, the two sperm plasma membrane marker enzymes. The differential enrichment and recovery of the sperm surface alpha-D-mannosidase is consistant with our previous studies in rat spermatozoa, and suggests that alpha-D-mannosidase may be localized on morphologically distinct region(s) of the sperm plasma membranes. The properties of human sperm surface alpha-D-mannosidase are quite similar to those reported by us for rat sperm plasma membrane mannosidase, but quite different from human sperm acid alpha-D-mannosidase. In addition, whereas anti-rat epididymal alpha-D-mannosidase antibody (IgG-fraction) cross-reacted with the human sperm acid alpha-D-mannosidase, no cross-reactivity was observed with the sperm surface mannosidase. A small amount of fucosyltransferase (less than 1% of the enzyme originally present on spermatozoa) was found in the salt-washed plasma membrane, but the enrichment of the enzyme was only one-tenth of that observed for adenylate cyclase. The potential ligand-like role of human sperm surface alpha-D-mannosidase and other sperm surface enzymes during fertilization is discussed.
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PMID:Human sperm plasma membranes possess alpha-D-mannosidase activity but no galactosyltransferase activity. 211 23

Plasma membranes were purified from flagella of porcine cauda epididymal sperm and proteolytic regulation of bicarbonate-sensitive adenylate cyclase was studied. It was found that the epididymal sperm plasma membrane contained a trypsin-like proteinase which inactivated adenylate cyclase. Bicarbonate activates adenylate cyclase as reported previously, but, at the same time, the anions enhance the inactivation of the enzyme by the membrane-bound trypsin-like proteinase. This phenomenon is not due to the direct activation of the proteinase, but closely related to the activation of adenylate cyclase by bicarbonate. It was also found that seminal proteinase inhibitors blocked the inactivation of adenylate cyclase and maintained the bicarbonate activation of the enzyme at high level. Actually, bicarbonate keeps adenylate cyclase fully active in ejaculated sperm, because membrane-bound proteinase is completely inhibited by the seminal proteinase inhibitors. These results suggest that the interactions between membrane-bound proteinase and seminal proteinase inhibitor are involved in the regulation of the bicarbonate-sensitive adenylate cyclase system.
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PMID:Effects of a membrane-bound trypsin-like proteinase and seminal proteinase inhibitors on the bicarbonate-sensitive adenylate cyclase in porcine sperm plasma membranes. 216 77

In this report we describe and partially characterize a preparation of digitonin-permeabilized guinea pig spermatozoa that undergo a rapid and synchronous modification of the acrosomal matrix in response to calcium. Permeabilization of cauda epididymal spermatozoa by digitonin was monitored by using adenylate cyclase activity as an indicator. Spermatozoa (5 x 10(7) cells) treated with 0.005% digitonin for 15 s exhibited maximal adenylate cyclase activity but generally retained their structural morphology, as examined by phase-contrast and transmission electron microscopy. The ratio fo cell number to detergent concentration was the critical factor for determining both the efficiency of permeabilization and the maintenance of structural integrity. When permeabilized spermatozoa were treated with 2 mM CaCl2, the cells underwent a rapid and synchronous modification of the acrosomal matrix (AM). As observed by phase-contrast microscopy, the response to CaCl2 was characterized by events that occurred in the following temporal sequence: disruption of the sperm rouleaux, the loss of refractility by the apical segment of the sperm acrosome, and detachment of the apical segment from the spermatozoa. Transmission electron microscopy indicated that the loss of refractility from the sperm apical segment was coincident with a calcium-induced dispersion of the AM. Analysis of the proteins released during this response, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealed that a specific subset of sperm proteins was released from the spermatozoa, including a major = staining, 45,000 Mr protein apparently generated from a higher molecular weight precursor during the acrosome reaction.
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PMID:Calcium-induced modification of the acrosomal matrix in digitonin-permeabilized guinea pig spermatozoa. 250 1

Gossypol administered orally to male rats at a daily dose of 20 mg/kg body weight for 62 days caused infertility. There were changes in the epididymal epithelium and the sperm were severely damaged and immotile. The sperm head was often detached; other defects were abnormal mitochondria, absence of plasma membranes and axonemal and accessory fibres and a lower oxygen uptake. To study the effect of gossypol on the motor apparatus of sperm, ram sperm were demembranated with the detergent, Triton-X-100. Such sperm models can normally be reactivated with ATP but gossypol (2.5-12.5 microM) decreased reactivation and must have a direct effect on the axoneme. Gossypol also inhibited ram sperm adenyl cyclase which is essential for maintaining high levels of cAMP in sperm and, in turn, motility. Ram sperm adenyl cyclase required Mn2+ for activity and high Mn2+ concentrations protected the enzyme from gossypol inhibition. Electron spin resonance studies proved that gossypol chelated Mn2+ with the formation of a 2:1 complex.
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PMID:Studies of the mechanism of action of gossypol as a male antifertility agent. 283 27


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