Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Buffalo sperm heads contain more than 50% of the total cyclic AMP-phosphodiesterase activity (EC 3.1.4.17) present in spermatozoa. Its distribution in sperm heads revealed no activity in acrosome and other membrane structures present in the head. All the cyclic AMP-phosphodiesterase activity was found firmly bound to sperm chromatin which could not be solubilized. In addition to cyclic AMP, cyclic GMP was also hydrolysed by chromatin preparation. The rate of hydrolysis was 2.5-times more rapid with cyclic AMP than with cyclic GMP at their optimum pH of 7.5 and 8.0, respectively. The pH and heat stability profiles, inhibition studies and the effect of divalent metal ions indicated that the two activities are not associated with the same protein. Mixed substrate analysis showed two sites at which the hydrolysis of cyclic AMP and cyclic GMP is catalysed. Chromatin cyclic nucleotide phosphodiesterases exhibited kinetics typical of one enzyme species both for cyclic AMP (K m = 100 microM; V = 1.0 nmol/min per mg protein) and cyclic GMP (Km = 23 microM; V = 0.4 nmol/min per mg protein). Each cyclic nucleotide was found to be a competitive inhibitor of the hydrolysis of the other with a Ki value of 30.18 microM for cyclic AMP hydrolysis and 256 microM for cyclic GMP hydrolysis. Hill coefficients of 1.0 obtained in the presence of cyclic AMP for cyclic GMP hydrolysis and vice-versa indicated no allosteric interactions. It is suggested that chromatin cyclic nucleotide phosphodiesterase may have a role post fertilization in cell growth and differentiation with no role in sperm motility which is regulated by similar enzymes present in sperm flagella.
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PMID:Association of cyclic nucleotide phosphodiesterase of buffalo spermatozoa with sperm chromatin. 626 50

The motility of human spermatozoa and its regulation were examined on cells isolated from other seminal components and purified into fractions of uniform progressive motility. The percent motile cells and estimates of their translational speed were determined by visual inspection, by stroboscopy, and by photon correlation spectroscopy; microcinematography and gradient centrifugation were occasionally used to clarify discrepancies. The motility of isolated spermatozoa could be maintained for periods up to 24 h at 4 or 37 degrees C; the presence of seminal fluid was not required and even provoked a reversible inhibition at 4 degrees C. Albumin facilitated cell movement between microscopic glass plates but had no effect on progressive motility per se, as evidenced by other techniques. During incubations of up to 2 h, progressive cell motility occurred independently of extracellular glucose and calcium but responded to variations in adenosine 3',5'-cyclic monophosphate and calcium. Dibutyryl cAMP increased forward motility, whereas ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid reversibly immobilized the spermatozoa in a calcium-dependent manner; phosphodiesterase inhibition resulted in increased vibration of sperm heads without any effect on progressive motility. Longer incubation periods required the presence of extracellular nutrients. These experiments further demonstrate that several motility measuring techniques should be used in parallel to distinguish the various components of cell movement, to exclude aspecific effects, and to supplement the shortcomings of each individual technique. Such procedure could clarify the various discrepancies that have been reported so far and should lead to a better understanding of the regulation of human sperm motility.
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PMID:Effect of temperature, nutrients, calcium, and cAMP on motility of human spermatozoa. 628 35

The activities of cAMP and cGMP phosphodiesterases (EC 3.1.4.1), adenylate cyclase (EC 4.6.1.1) and protein carboxyl-methylase (EC 2.1.1.24) were measured in the particulate and soluble (105 000 g supernatant) fractions of washed spermatozoa isolated from five segments of the adult rat epididymis. The activities of both phosphodiesterases decreased during epididymal transit, whereas adenylate cyclase and protein carboxyl-methylase underwent a progressive increase, the latter showing the most marked alteration. Both cAMP and cGMP phosphodiesterases as well as the adenylate cyclase were all associated primarily with the particulate fraction, and the extent to which these enzymes were associated with the membranes increased as the spermatozoa passed through the epididymis. Sperm protein carboxyl-methylase activity was, on the other hand, predominantly soluble in all segments of the epididymis. Adenylate cyclase, cAMP phosphodiesterase and protein carboxyl-methylase activities were found predominantly in the sperm tails, whereas cGMP phosphodiesterase was equally distributed between heads and tails. These observations imply that the acknowledged increase in intracellular cAMP levels which occurs in spermatozoa during epididymal transit may be a consequence of both increased synthesis (adenylate cyclase) and reduced hydrolysis (phosphodiesterase).
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PMID:Rat sperm enzymes during epididymal transit. 628 32

In sonicated human spermatozoa, phosphodiesterase hydrolyzed adenosine 3':5'-monophosphate (cAMP) at 20.80 +/- 3.23 nmoles/10(8)sperm/20 min at 37 degrees C (50 microM cAMP, initially). In human semen, about 60% of the phosphodiesterase activity was in the spermatozoa. Both polyacrylamide gel electrophoresis and DEAE-cellulose column chromatography indicated that there are at least 5 isozymes of phosphodiesterase. Various steroids were tested at a concentration of 2 micrograms/ml for their effects on phosphodiesterase activity in semen. None was found to have any significant effect. In sonicated human spermatozoa, adenylate cyclase synthesized cAMP at 0.02-2.11 nmoles/10(8)sperm/20 min at 37 degrees C (1 mM ATP, initially) depending on the availability of Mn2+ and caffeine in the assay mixture. Mn2+ was demonstrated to be a potent adenylate cyclase activator in human spermatozoa and its effect on human sperm adenylate cyclase was found to be dose-dependent. Cholera toxin, at a concentration of 20 micrograms/ml, had no effect on human sperm adenylate cyclase activity after it had been incubated with the intact spermatozoa for between 5 min and 5 h at 37 degrees C before the sperm were homogenized and the rate of cAMP formation assayed. In addition, human sperm adenylate cyclase decayed rapidly at 37 degrees C. Of various steroids tested at a concentration of 2 micrograms/ml for their effects on human sperm adenylate cyclase activity, only oestradiol-17 beta showed a significant effect, elevating the rate of cAMP formation by about 30%.
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PMID:Partial characterization of human spermatozoal phosphodiesterase and adenylate cyclase and the effect of steroids on their activities. 628 74

Rabbit sperm pyruvate kinase remains bound to the cell structure of hypotonically treated mature rabbit epididymal spermatozoa (HTRES). It displays kinetic behavior very similar to that of rabbit muscle pyruvate kinase with regard to KM values for substrates, activation by monovalent and divalent cations, inhibition by phenylalanine which is reversed by alanine, and lack of activation by fructose-1,6-biphosphate. The flagellar ATPase also remains bound to the cell structure of HTRES, whose motility may be reactivated by a source of ATP. It requires Mg+2 for activity; the KM for both ATP and MG+2 is 0.2 mM, implying that MgATP is the substrate. The ATPase activity is not inhibited by ouabain, oligomycin, or vanadate, which also do not affect reconstituted motility, and is not affected by cyclic AMP in the presence of an inhibitor of phosphodiesterase. The activities of pyruvate kinase and the flagellar ATPase in a given preparation of HTRES are comparable. Rabbit spermatozoa have a metabolic strategy which is very similar to muscle cells. This suggests that the major use of the sperm cell's metabolic machinery is maintenance of energy for the contractile work of motility and that only minor amounts of metabolic energy appear to be consumed in other reactions, including those involved in fertilization.
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PMID:Properties of pyruvate kinase and flagellar ATPase in rabbit spermatozoa: relation to metabolic strategy of the sperm cell. 644 94

Sperm surface changes during in vitro capacitation were examined with the help of an assay system using lectin-coated agarose beads. The nature and intensity of binding of epididymal spermatozoa to beads depended entirely on the particular stage of capacitation and the type of lectin attached to the bead surface. Fresh epididymal spermatozoa bound readily to beads coated with Con A, LCA, WGA, and PNA, but not with seven other lectins. During capacitation there was a constant decline in sperm binding to beads, and spermatozoa cultured for 4-5 hr bound only to those coated with Con A. A dramatic increase in sperm binding to Con A-coated agarose beads occurred between 4.5 and 5 hr, when large numbers of hyperactivated spermatozoa adhered, predominantly through their flagellae, to form large clumps on the beads. The clumping of spermatozoa on Con A-coated beads was enhanced in the presence of stimulators of capacitation (i.e., taurine, hypotaurine, and phosphodiesterase inhibitors) and was suppressed in the presence of various metabolic inhibitors (i.e., sodium azide and local anesthetics). The implications of these results are that the carbohydrate components of the entire surface of spermatozoa undergo striking changes during capacitation, and a close relationship may exist between the sperm surface and the metabolic changes occurring within capacitating spermatozoa. Sperm-bead binding assays are clearly able to recognize surface changes in asynchronous populations of motile spermatozoa and, due to their simplicity and speed, should prove to be valuable in gaining a greater understanding of the biochemistry of sperm capacitation.
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PMID:Lectin-coated agarose beads in the investigation of sperm capacitation in the hamster. 673 31

Live trout spermatozoa initiate flagellar motility for only a short period (30 sec at 18 degrees C) during which their mean beat frequency decreases steadily from 60 to 20 Hz. Motility then stops abruptly. Investigations of the activation of movement in demembranated sperm points to cyclic-AMP being necessary for reactivation (half effect at 0.5 microM) in some conditions. cAMP acts mainly by increasing the percentage of motile cells and not the beat frequency (BF) of the flagellar axoneme. Dibutyryl cAMP does not initiate movement or prolong motility of live sperm. The initiation of movement of demembranated trout sperm was investigated in various incubation conditions relative to previous phases of in vivo movement and to ATP concentration. In the absence of cAMP and in the presence of ATP lower than 25 microM, all sperm cell models were active with BF up to 15-20 Hz whatever their previous physiological conditions. In contrast, at ATP concentrations above 100 microM, the fraction of active spermatozoa decreased proportionally but the BF of the active ones increased so that, at 1 mM ATP, only 5% were active but with a BF of 65 Hz: the addition of cAMP up to 20 microM restored activity to 100% sperm models with a similar BF of 65 Hz. At ATP concentrations higher than 25 microM, cAMP was necessary in a concentration dependent manner in the reactivation, but not in the demembranation medium. This dependence was found to be unrelated to a previous in vivo phase of movement. The antagonistic effects of ATP vs. cAMP were tested at various concentrations of both nucleotides: the apparent affinity for cAMP, measured as the concentration restoring movement of 50% cell models, was decreased from 15 nM at 0.1 mM ATP to 0.5 microM at 1 mM ATP; conversely, the affinity for ATP, measured as the concentration giving rise to the half maximal beat frequency, was not significantly affected when the concentration of cAMP was raised to 0.5 mM. Preincubation with phosphodiesterase (PDE) resulted in motility of 100% of sperm models even at low ATP concentration. This tends to show that cAMP must be constantly present to sustain motility.
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PMID:cAMP/ATP relationship in the activation of trout sperm motility: their interaction in membrane-deprived models and in live spermatozoa. 755 9

Treatment of spermatozoa with 10 mM caffeine increases the rotational mobility of thiol-containing proteins in a defined micellar micro-environment. This is associated with inhibition of superoxide dismutase activity and augmented superoxide anion radical generation. Increased sperm competence in presence of caffeine in human oligospermia is explained by these observations. Inhibition of cyclic phosphodiesterase by caffeine is suggested to be part of the observed lattice-rearrangement.
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PMID:Methyl xanthine and altered biomembrane dynamics: demonstration of protein mobility and enzyme inhibition by caffeine in sperm model system. 819 98

Data are presented covering various studies on the use of the phosphodiesterase inhibitor pentoxifylline (PF) in the sperm preparation for procedures in assisted reproduction. Significant improvements have been shown in the fertilization rate of oocytes along with a reduced risk of failed fertilization cycles utilizing oligo/asthenozoospermic semen samples. Fertilization is also improved for normozoospermic samples when the acrosome reaction is suboptimal. PF has proven effects on sperm motility, increasing the proportion of hyperactivated spermatozoa. It can also enhance the acrosome reaction and this may be the more relevant function for clinical prediction. There is a further action as a suppressor or scavenger of reactive oxygen species although higher concentrations than that in current clinical use may be required to optimize this effect. PF should be washed out of the sample used for insemination to avoid inhibiting the completion of oocyte maturation.
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PMID:Pentoxifylline: actions and applications in assisted reproduction. 828 39

Boar spermatozoa loaded with the Ca2+ probe fluo-3 were incubated in various Tyrode's-based media similar to those used for in vitro fertilization (IVF), and samples were then analysed by two-colour flow cytometry; propidium iodide was included in the media to detect membrane-damaged ("dead") cells. If media contained bicarbonate/CO2 (a component thought to promote capacitation), part of the live sperm population experienced a considerable influx of Ca2+ into both head and tail compartments. The percentage of responding cells reached a maximum after about 30 min, but both during and after this period there was also a steady increase in the number of dead cells. This bicarbonate-mediated increase in cell death took place in the absence of external Ca2+. Evidence was obtained that the entry of propidium iodide was preceded by a change in permeability of the plasma membrane, detectable by leakage of carboxydichlorofluorescein, and it was therefore deduced that the Ca2+ influx detected by fluo-3 was due to destabilization of the plasma membrane. A similar response could be produced by both caffeine and papaverine (best known as phosphodiesterase inhibitors), but neither cyclic AMP nor activators of adenylate cyclase had any effect. There was no influence of substrate on the process, but, in comparison to poly(vinyl alcohol), serum albumin enhanced it. The precise relevance of this destabilization to capacitation is not yet clear, but it seems significant that the process is mediated or enhanced by components often specifically included in IVF media, and that different individual cells respond after different times.
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PMID:Flow cytometric studies of bicarbonate-mediated Ca2+ influx in boar sperm populations. 839 Dec 78


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