UNIPROT:P47989 - FACTA Search

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Query: UNIPROT:P47989 (xanthine oxidase)
8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Semenogelin (Sg), the major protein of the human semen coagulum, is present at high concentrations in seminal vesicle secretions. It is degraded by the prostate-specific antigen (PSA) to generate peptides of various biological activities that were found on and inside spermatozoa. Our aim was to determine the effect of Sg on capacitation, which is the series of transformations that spermatozoa must undergo to become fertile. At concentrations of 0.1 to 1.0 mg/mL (600- to 20-fold lower than those of semen), Sg did not affect sperm motility (%) but completely prevented capacitation induced by fetal cord serum ultrafiltrate; a partial inhibition of capacitation was noted with 0.03 mg Sg/mL. There was also a dose-dependent decrease in the tyrosine phosphorylation of fibrous sheath proteins and in the O2-.-related chemiluminescence. Ribonuclease (RNase), which has as high an isoelectric point (pI = 9.7) as Sg (pI = 9.5), also prevented sperm capacitation and O2-.-related chemiluminescence but to a lower extent, suggesting that one mechanism of Sg action on spermatozoa could be related to its positive charge at physiological pH. Sg at 1, but not 0.3 or 0.1 mg/mL, scavenged the O2-. generated by the mix of xanthine + xanthine oxidase and modified the kinetics of the reaction; RNase did not have such effects. Therefore, Sg is a potential scavenger for O2-. but probably also affects the sperm oxidase. Spermatozoa rapidly processed Sg; a high proportion of Sg was degraded after 15 minutes of incubation. The resulting polypeptide patterns were reminiscent of those obtained with PSA as a proteolytic enzyme. These data suggest that Sg, its degradation products, or both may be natural regulators of sperm capacitation and could prevent this process from occurring prematurely. One mechanism by which Sg acts could involve an interference with the O2-. that is normally generated during this process.
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PMID:Semenogelin, the main protein of semen coagulum, inhibits human sperm capacitation by interfering with the superoxide anion generated during this process. 1145 65

Improvement of bovine semen cryopreservation requires a better understanding of the properties of the currently used extenders. At present, about half of the spermatozoa die or become immotile following cryopreservation. The implication of an oxidative stress during or following the process of cryopreservation has been suspected to alter sperm functions. However, insufficient information is available on the effect of oxidative stress on sperm functions in their surrounding environment, the extender, such as the one based on egg yolk, Tris and glycerol. In this study, we investigated the effects of hydrogen peroxide (H2O2) and superoxide anion (O2*-) on bovine sperm motility in a widely used egg yolk Tris glycerol (EYTG) extender in comparison to a reference medium, the Tyrode's albumen lactate pyruvate (TALP). Bovine sperm were incubated for 6 h with or without concentrations of H2O2 ranging from 12.5 microM to 1.25 mM and with the hypoxanthine/xanthine oxidase system (X/XOD) that generates O2*-. Sperm motility was established by computer assisted semen analysis (CASA) in four similar experiments using the same frozen pool of semen. We have found that sperm motility was reduced significantly by H2O2 concentrations 20-fold lower in EYTG than in TALP medium. The differential resistance of the two media was explained by pyruvate present in TALP that acts as an antioxidant and metals ions, chelated by ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DETAPAC), found in egg yolk that might react with H2O2. Addition of only 5 U/ml of bovine liver catalase or oviductal fluid catalase (OFC) were sufficient to overcome the loss of sperm motility caused by 100 microM H2O2 in both EYTG and TALP. However, OFC was the most effective of the two catalases in EYTG. In addition to maintain sperm motility, catalase (5 U/ml) and pyruvate (5 mM) increased the intracellular sperm ATP level in comparison to sperm incubated alone for 6 h at 38.5 degrees C in EYTG. Moreover, EDTA, pyruvate and catalase prevented sperm ATP loss in presence of 100 mM of H2O2 in EYTG. These results indicated that EYTG has a very limited capacity to neutralize H2O2, and the addition of low amounts of catalase and millimolar concentrations of pyruvate greatly improved the antioxidant properties of a commonly used extender.
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PMID:Reactive oxygen species-mediated loss of bovine sperm motility in egg yolk Tris extender: protection by pyruvate, metal chelators and bovine liver or oviductal fluid catalase. 1204 4

Human spermatozoa are highly susceptible to oxidative injury but are naturally protected from such injury by the antioxidant properties of seminal plasma. We measured catalase-like and superoxide dismutase (SOD)-like activities in the seminal plasma of fertile and vasectomized men in order to gain insight into the potential source(s) and function(s) of these antioxidants in semen. Semen samples were obtained from fertile men ( n=11) and men post-vasectomy ( n=16). Catalase-like activity was measured by the decrease in hydrogen peroxide concentration after incubation with seminal plasma. SOD-like activity was measured as the inhibition of nitroblue tetrazolium reduction due to superoxide anion generation by xanthine plus xanthine oxidase. Mean seminal catalase-like activity (+/-1SD) in the fertile group was not significantly different from that of the post-vasectomy group (389+/-163 and 325+/-119 U/ml, respectively). Similarly, mean seminal SOD-like activity in the fertile group was not significantly different from that of the post-vasectomy group (37+/-10 and 36+/-10 U/ml, respectively). Our data suggest that the testis and epididymis are not an important source of catalase-like and SOD-like activities in semen. These findings indicate that antioxidants in semen are primarily of post-testicular origin and probably serve to protect ejaculated spermatozoa from oxidative stress such as that which occurs in the female reproductive tract.
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PMID:Catalase-like and superoxide dismutase-like activities in human seminal plasma. 1238 21

The objective of this study was to examine the effect of reactive oxygen species (ROS) and cryopreservation on DNA fragmentation of equine spermatozoa. In experiment 1, equine spermatozoa were incubated (1 hour, 38 degrees C) according to the following treatments: 1) sperm alone; 2) sperm + xanthine (X, 0.3 mM)-xanthine oxidase (XO, 0.025 U/mL); 3) sperm + X (0.6 mM)-XO (0.05 U/mL); and 4) sperm + X (1 mM)-XO (0.1 U/mL). In experiment 2, spermatozoa were incubated (1 hour, 38 degrees C) with X (1 mM)-XO (0.1 U/mL) and either catalase (200 U/mL), superoxide dismutase (SOD, 200 U/mL), or reduced glutathione (GSH, 10 mM). Following incubation, DNA fragmentation was determined by the single cell gel electrophoresis (comet) assay. In experiment 3, equine spermatozoa were cryopreserved, and DNA fragmentation was determined in fresh, processed, and postthaw sperm samples. In experiment 1, incubation of equine spermatozoa in the presence of ROS, generated by the X-XO system, increased DNA fragmentation (P <.005). In Experiment 2, the increase in DNA fragmentation associated with X-XO treatment was counteracted by the addition of catalase and GSH but not by SOD, suggesting that hydrogen peroxide and not superoxide appears to be the ROS responsible for such damage. In experiment 3, cryopreservation of equine spermatozoa was associated with an increase (P <.01) in DNA fragmentation when compared with fresh or processed samples. This study indicates that ROS and cryopreservation promote DNA fragmentation in equine spermatozoa; the involvement of ROS in cryopreservation-induced DNA damage remains to be determined.
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PMID:Reactive oxygen species and cryopreservation promote DNA fragmentation in equine spermatozoa. 1282 2

The objective of this study was to examine the influence of reactive oxygen species (ROS) on equine sperm capacitation. Motile equine spermatozoa were separated on a discontinuous Percoll gradient, resuspended at 10 x 10(6)ml in Tyrode's medium supplemented with BSA (0.5%) and polyvinyl alcohol (0.5%) and incubated at 39 degrees C for 2h with or without the xanthine (X; 0.1mM)-xanthine oxidase (XO; 0.01 U/ml) system or NADPH (0.25 mM). The importance of hydrogen peroxide or superoxide for capacitation was determined by the addition of catalase (CAT; 150 U/ml) or superoxide dismutase (SOD; 150 U/ml), respectively. Following incubation, acrosomal exocytosis was induced by a 5 min incubation at 39 degrees C with progesterone (3.18 microM), and sperm viability and acrosomal integrity were then determined by staining with Hoechst 33258 and fluoroisothiocyanate-conjugated Pisum sativum agglutin. To examine tyrosine phosphorylation, treatments were subjected to sodium dodecyl sulfate-polyacrylaminde gel electrophoresis (SDS-PAGE) followed by Western blot analysis with the anti-phosphotyrosine antibody (alpha-PY; clone 4G10). Capacitation with the X-XO system or NADPH led to a significant (P<0.0001) increase in live acrosome-reacted spermatozoa compared to controls. The addition of CAT or SOD prevented the increase in live acrosome-reacted spermatozoa associated with X-XO treatment. Incubation with the X-XO system was also associated with a significant (P<0.005) increase in tyrosine phosphorylation when compared to controls, which could be prevented by the addition of CAT but not SOD. This study indicates that ROS can promote equine sperm capacitation and tyrosine phosphorylation, suggesting a physiological role for ROS generation by equine spermatozoa.
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PMID:Reactive oxygen species promote tyrosine phosphorylation and capacitation in equine spermatozoa. 1451 78

Glutathione peroxidase is one of the principal antioxidant defense enzymes in human spermatozoa, but it requires oxidized glutathione to be reduced by glutathione reductase using NADPH generated in the pentose phosphate pathway. We investigated whether flux through the pentose phosphate pathway would increase in response to oxidative stress and whether glutathione reductase was required to protect sperm from oxidative damage. Isotopic measurements of the pentose phosphate pathway and glycolytic flux, thiobarbituric acid assay of malondialdehyde for lipid peroxidation, and computer-assisted sperm analysis for sperm motility were assessed in a group of normal, healthy semen donors. Applying moderate oxidative stress to human spermatozoa by adding cumene hydroperoxide, H(2)O(2), or xanthine plus xanthine oxidase or by promoting lipid peroxidation with ascorbate increased flux through the pentose phosphate pathway without changing the glycolytic rate. However, adding higher concentrations of oxidants inhibited both the pentose phosphate pathway and glycolytic flux. At concentrations of 50 microg/ml or greater, the glutathione reductase-inhibitor 1,3-bis-(2-chloroethyl) 1-nitrosourea decreased flux through the pentose phosphate pathway and blocked the response to cumene hydroperoxide. It also increased lipid peroxidation and impaired the survival of motility in sperm incubated under 95% O(2). These data show that the pentose phosphate pathway in human spermatozoa can respond dynamically to oxidative stress and that inhibiting glutathione reductase impairs the ability of sperm to resist lipid peroxidation. We conclude that the glutathione peroxidase-glutathione reductase-pentose phosphate pathway system is functional and provides an effective antioxidant defense in normal human spermatozoa.
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PMID:Functional significance of the pentose phosphate pathway and glutathione reductase in the antioxidant defenses of human sperm. 1518 35

It has been shown recently that African catfish (Clarias gariepinus) spermatozoa possess relatively low ATP content and low adenylate energy charge (AEC). One of the possible explanations for this phenomenon is that the spermatozoa actively catabolize adenine nucleotides. A relatively high rate of such catabolism could then contribute to the low ATP concentration and low adenylate energy charge observed in the spermatozoa in vitro. To check this hypothesis, we investigated ATP content and adenine nucleotide catabolism in African catfish spermatozoa stored at 4 degrees C in the presence of glycine as an energetic substrate. Our results indicate that the storage of African catfish sperm at 4 degrees C in the presence of glycine causes time-dependent ATP depletion. In contrast to ATP, the AMP content increases significantly during the same period of sperm storage, while the ADP increases only slightly. Moreover, a significant increase of inosine and hypoxanthine content was also found. Hypoxanthine was accumulated in the storage medium, but xanthine was found neither in spermatozoa nor in the storage medium. It indicates that hypoxanthine is not converted to xanthine, probably due to lack of xanthine oxidase activity in catfish spermatozoa. Present results suggest that adenine nucleotides may be converted to hypoxanthine according to the following pathway: ATP-->ADP-->AMP (adenosine/IMP)-->inosine-->hypoxanthine. Moreover, hypoxanthine seems to be the end product of adenine nucleotide catabolism in African catfish spermatozoa. In conclusion, our results suggest that a relatively high rate of adenine nucleotide catabolism contributes to the low ATP concentration and low adenylate energy charge observed in African catfish spermatozoa in vitro.
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PMID:In vitro adenine nucleotide catabolism in African catfish spermatozoa. 1532 39

A range of compounds with a role in oxidative stress were measured in ejaculates from 40 normozoospermic individuals and 93 infertile males. Ejaculates were classified according to WHO criteria. Seminal plasma and the sperm cell fraction were assessed separately for superoxide dismutase (SOD), catalase, xanthine oxidase, capability for singlet oxygen trapping and content of thiobarbituric acid-reactive substances (TBARS). Pathological cases defined as oligozoospermia, asthenozoospermia, or teratozoospermia revealed different backgrounds of oxidative stress as reflected by different levels of tested substances in every type of sperm pathology. In the majority of abnormal ejaculates, a significant increase in intracellular activity of SOD, decreased intracellular levels of catalase, elevated levels of xanthine oxidase and TBARS, and severely impaired singlet oxygen trapping were observed when compared to normozoospermic ejaculates. Interrelationships between SOD and TBARS, and between xanthine oxidase and catalase, appeared to be of key importance when analysed separately in seminal plasma and in spermatozoa or in a combination of both. Elevated xanthine oxidase levels and low capacity for singlet oxygen trapping are statistically significant factors for the evaluation of male infertility which can develop as a result of persistent oxidative stress.
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PMID:Effect of reactive oxygen species and the activity of antioxidant systems on human semen; association with male infertility. 1613 Feb 69

Capacitation is part of an oxidative process necessary for bovine spermatozoa to acquire fertilizing capacity. This process includes the generation of reactive oxygen species (ROS) and the participation of protein kinases such as A (PKA), C (PKC) and tyrosine kinase (PTK). A redox status is required to support both sperm motility and capacitation. Our aim was to determine the requirement of lactate dehydrogenase C4 (LDH-C4) and isocitrate dehydrogenase (NADP-ICDH) and of protein kinases in cryopreserved bovine sperm capacitation. The presence of inhibitors of both LDH-C4 and NADP-ICDH prevented the heparin-induced capacitation. H89, GF109203X or genistein blocked capacitation triggered by heparin or the superoxide (O(-*)(2))generator system xanthine-xanthine oxidase-catalase (XXOC) suggesting the requirement of PKA, PKC and PTK in this process. Taken together these results suggest that LDH-C4 and NADP-ICDH contribute with the redox status to support bovine sperm capacitation and that PKA, PKC and PTK are involved in different mechanisms induced by different inducers that lead bovine spermatozoa to be capacitated.
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PMID:Heparin- and superoxide anion-dependent capacitation of cryopreserved bovine spermatozoa: requirement of dehydrogenases and protein kinases. 1651 8

Low-level production of the superoxide anion (O2*-) is an important signal transduction event in sperm function including capacitation; however, excessive production of O2*- can be detrimental to sperm function. The objective of this study was to assess dihydroethidium (DHE) as a probe for O2*- in equine spermatozoa. Ejaculated spermatozoa were separated by centrifugation over a Percoll gradient (40:80), and loaded with DHE (2.0 microM) as well as with calcein-acetoxymethylester (CAM, 7.8 nM) to determine cell viability. In Experiment 1, cells were incubated with the xanthine-xanthine oxidase (X, 0.1 mM; XO, 0.01 U/mL) generating system for the production of O2*-, with or without the addition of superoxide dismutase (SOD, 150 U/mL) or the SOD mimetic, Tiron (0.1, 1.0 or 5.0 mM) for 1h. Changes in fluorescence of DHE were determined for the live cell population (calcein-positive cells) by flow cytometry. The DHE fluorescence increased with the X-XO incubation; this increase was inhibited by SOD or Tiron, indicating that DHE is specific for O2*- detection. In Experiment 2, spermatozoa were loaded with DHE/CAM, treated with calcium ionophore A23187 (0, 0.8, or 8.0 microM), and incubated for 15 min. Cell fluorescence was again determined by flow cytometry. Calcium ionophore A23187 increased O2*- production in a dose-dependent manner. In Experiment 3, cells were loaded with DHE/CAM, treated with NADPH (0.0, 0.25, 0.5, or 1 mM) with or without 0.5% Triton X-100, and incubated for 15 min prior to flow cytometry. Cells treated with NADPH with or without 0.5% Triton X-100 did not have O2*- levels that were significantly different from the control. In Experiment 4, spermatozoa loaded with DHE/CAM were incubated under capacitating conditions (1.2 mM dibutryl-cAMP+1.0 mM caffeine) or in control media for 3h. Although O2*- generation increased over time in control and capacitated treatments, spermatozoa incubated under capacitating conditions had higher O2*- production than those incubated in control media. Therefore, DHE was a useful probe for the detection of O2*- in equine spermatozoa and elevation in intracellular calcium as well as capacitation in vitro were associated with increased generation of O2*-.
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PMID:Generation of superoxide anion by equine spermatozoa as detected by dihydroethidium. 1704 38

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