UNIPROT:P56851 - FACTA Search

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Query: UNIPROT:P56851 (epididymal)
11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Vitro binding and some binding parameters of the glycosaminoglycan heparin to viable epididymal or ejaculated bull spermatozoa, ejaculated rabbit spermatozoa, and frozen-thawed rhesus monkey spermatozoa were investigated. Nonspecific binding was affected only by the concentration of 3H-heparin, whereas specific binding was saturable, reversible, and dependent on the pH, temperature, and calcium concentration of the incubation medium. Magnesium concentration dependence was observed in the presence of calcium but could not be detected in the absence of calcium. Bound 3H-heparin was displaced by several orders of magnitude greater concentrations of chondroitin sulfate. Scatchard plot analysis suggested multiple binding affinities for 3H-heparin to spermatozoa. 3H-heparin was shown to bind to sperm heads and flagella. Fluorescein-labeled heparin bound to acrosomal, postacrosomal, and flagellar membranes. It was concluded that the specific binding of heparin involved a proteinaceous component on, or intercalated with, spermatozoal membranes. Thus, glycosaminoglycans present in the female reproductive tract may contribute to sperm capacitation and enhance the likelihood of successful fertilization in mammals.
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PMID:Specific binding of the glycosaminoglycan 3H-heparin to bull, monkey, and rabbit spermatozoa in vitro. 671 57

1. Increasing concentrations of both Ca2+ and Sr2+ (generated by using EGTA buffers) resulted in 4-fold increases in the initial activity of pyruvate dehydrogenase within intact uncoupled mitochondria from rat epididymal adipose tissue incubated in the presence of the ionophore A23187, ATP, Mg2+ and oligomycin. The k0.5 values (concentrations required for half-maximal effects) for Ca2+ and Sr2+ were 0.54 and 7.1 microM respectively. In extracts of the mitochondria, pyruvate dehydrogenase phosphate phosphatase activity was stimulated about 4-fold by Ca2+ and Sr2+, with k0.5 values of 1.08 and 6.4 microM respectively. 2. NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase appeared to be rate-limiting in the oxidation of threo-Ds-isocitrate and oxoglutarate by uncoupled mitochondria from brown adipose tissue of cold-adapted rats. Ca2+ (and Sr2+) diminished the Km for the oxidation of both threo-Ds-isocitrate and oxoglutarate. The kinetic constants for these oxidations were very similar to those obtained for the activities of NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase in extracts of the mitochondria. In particular, the k0.5 values for Ca2+ were all in the range 0.2--1.6 microM and Sr2+ was found to mimic Ca2+, but with k0.5 values about 10 times greater. 3. Overall, the results of this study demonstrate that the activities of pyruvate dehydrogenase, NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase may all be increased by Ca2+ and Sr2+ within intact mitochondria. In all cases the k0.5 values are close to 1 and 10 microM respectively, as found for the separated enzymes. Experiments on brown-adipose-tissue mitochondria incubated in the presence of albumin suggest that it may be possible to use the sensitivity of the dehydrogenases to Ca2+ as a means of assessing the distribution of Ca2+ across the mitochondrial inner membrane.
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PMID:Role of calcium ions in the regulation of intramitochondrial metabolism. Properties of the Ca2+-sensitive dehydrogenases within intact uncoupled mitochondria from the white and brown adipose tissue of the rat. 677 77

Epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase), the enzyme that catalyses the conversion of testosterone into the biologically active metabolite dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one), is a membrane-bound enzyme found in both nuclear and microsomal subcellular fractions. In order to characterize epididymal delta 4-steroid 5 alpha-reductase, it was first necessary to solubilize the enzymic activity. Of the various treatments tested, a combination of 0.5% (w/v) Lubrol WX, 0.1 M-sodium citrate and 0.1 M-KCl maintained enzymic activity at control values and solubilized 66% of total epididymal delta 4-steroid 5 alpha-reductase activity in an active and stable form. The sedimentation coefficient of solubilized delta 4-steroid 5 alpha-reductase, as determined in continuous sucrose density gradients, was greater for the microsomal than for the nuclear enzyme (11.6S compared with 10.1S). Although the apparent Km values of the enzyme for testosterone were similar in nuclear and microsomal subcellular fractions (range 1.75 x 10(-7) - 4.52 x 10(-7)M), the apparent Km of the enzyme for NADPH was about 30-fold greater for the microsomal enzyme than for the nuclear enzyme. The apparent Km of the enzyme for either substrate was not significantly altered after solubilization. The relative capacity of steroids to inhibit the enzymic activity, the pH optima and the effects of Ca2+ and Mg2+ were similar for membrane-bound and solubilized delta 4-steroid 5 alpha-reductase in both the nuclear and the microsomal fractions. The results reported demonstrate that epididymal delta 4-steroid 5 alpha-reductase can be solubilized in an active and stable form with no significant changes in the kinetic characteristics of the enzyme after solubilization; furthermore, kinetic and molecular-size differences observed for the nuclear and the microsomal forms of the enzyme suggest that there may exist at least two forms of epididymal delta 4-steroid 5 alpha-reductase.
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PMID:Solubilization and partial characterization of rat epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase). 687 Aug 29

The role of intracellular signal transduction mechanisms in regulating the motility and metabolism of rat spermatozoa in undiluted caudal epididymal fluid (CEF) was examined. Samples of CEF containing immotile spermatozoa were exposed to drugs and other agents that either stimulate signal transduction pathways or mimic the action of their second messengers. Under these conditions, sperm motility in 25-30 nl of CEF was stimulated by calcium ions (Ca2+), N2,2'-O-dibutyrylguanosine 3':5'-cyclic monophosphate (dibutyryl cGMP), cyclic adenosine 3':5'-monophosphate (cAMP), N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dibutyryl cAMP), 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo cAMP), caffeine, theophylline and bicarbonate ions (HCO3-). Other agents such as magnesium ions (Mg2+), veratridine, phospholipase C (PLC), ionophore A23187, 1,2-dioctenoyl-sn-glycerol (DAG), phorbol 12-myristate 13-acetate, phospholipase A2 (PLA2), arachidonic acid, and melittin did not significantly influence motility. In the presence of radiolabelled energy substrates, untreated (immotile) spermatozoa in samples of CEF utilised D-[U-14C]glucose and [1-14C]acetate as exogenous energy sources for oxidative metabolism. No detectable 14C-lactate was produced, and none of the drugs altered the rate of glycolytic or oxidative metabolism. The findings suggest that the motility of rat caudal epididymal spermatozoa is regulated by Ca2+ and the guanylate cyclase and adenylate cyclase pathways, but not through the PLC and PLA2 pathways. Also, their metabolism of exogenous substrate was uncoupled from the induction of motility, and their oxidative capacity exceeded the rate of flux of glucose-carbon through the glycolytic pathway.
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PMID:Intracellular signal transduction mechanisms of rat epididymal spermatozoa and their relationship to motility and metabolism. 804 68

Since cAMP is considered to play a major role in the acquisition of maturation and fertilizing capacity of mammalian sperm, we investigated the expression of cAMP-synthesizing adenylyl cyclase (AC) in sperm retrieved directly from the human epididymis. Particulate fractions were prepared from purified epididymal sperm samples and AC was monitored by the direct conversion of ATP into cAMP. We report that in great contrast to human ejaculated sperm and other mammalian sperm cells, the human epididymal sperm do not express a Mn(2+)-sensitive AC. However, a functional AC was readily detectable in these sperm cells in the presence of saturating concentrations of Ca2+ (50mM) and bicarbonate (HCO3-, 50mM), a combination that causes maximal activation in human ejaculated sperm. Using these conditions, human epididymal sperm AC showed similar capacity to generate cAMP compared to human ejaculated sperm AC. When assays were performed in the presence of Mg2+ and a saturating concentration of GMP-P(NH)P (50 microM), the hydrolysis-resistant GTP analog, and forskolin (100 microM), no activity was detected indicating that the epididymal sperm AC differs from that in somatic cells. These data demonstrate that human epididymal sperm contain an AC that is unique and different from the enzyme system described in somatic cells and other mammalian sperm cells, including human ejaculated sperm.
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PMID:Evidence for a novel adenylyl cyclase in human epididymal sperm. 824 32

The activity of adipose tissue hormone-sensitive lipase in animals with hyperinsulinemia has been reported to be increased compared with that in control animals. We examined whether this results from a direct effect of insulin on the tissue and whether it is accompanied by alteration in the regulation of lipolysis. When rat epididymal fat pads are incubated in culture medium with bovine serum albumin for 2-4 h with 2 ng/ml or 50 microU/ml of insulin, hormone-sensitive lipase activity in the postmicrosomal supernatant fraction after acid precipitation and activation with ATP-Mg2+ increases significantly compared with preparations from tissues incubated with the vehicle. The specific activities of hormone-sensitive lipase in sonicates of adipocytes after primary culture with insulin at concentrations from 10 to 4000 ng/ml (250 microU to 100 mU/ml) increase in an insulin-dose-related manner. Lipolysis in response to 10(-7) M isoproterenol also increases in an insulin-dose-dependent manner. Enhancement of isoproterenol-mediated lipolysis is not attributable to a difference in the triglyceride content of the cells. Lipolysis caused by the beta-agonist could be completely blocked by the simultaneous presence of insulin in both control and insulin-treated cells reflecting normal responsiveness of both types of cells to the acute effect of insulin. Although an increase in lipolysis is seen with norepinephrine and growth hormone after insulin treatment, other lipolytic agents such as ACTH, thyrotropin, and glucagon evoke similar responses in insulin-treated and control cells. The simultaneous presence of growth hormone and insulin during the 16-h culture results in additive effects on the subsequent response of the cells to 10(-7) M isoproterenol compared with the responses of the cells cultured with each hormone alone. beta-Agonist-mediated cAMP accumulation in the presence of Ro-20.1724, a specific phosphodiesterase inhibitor, is significantly higher in cells cultured in the presence of insulin than in control cells. Forskolin (1-25 microM) increases the lipolytic responses of insulin-treated cells compared with control cells, but the maximal response of the insulin-treated cells to forskolin is lower than that to isoproterenol. We conclude that changes produced by chronic insulin treatment involve more than one site along the lipolytic cascade.
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PMID:Chronic exposure of rat fat cells to insulin enhances lipolysis and activation of partially purified hormone-sensitive lipase. 839 27

We have recently demonstrated multiple fucosyltransferase (FT) activity in rat spermatogenic cells. To complement these findings, here we identify and partially characterize the glycosidic linkage specificity of FTs present in spermatozoa from caput and cauda epididymides. Analysis of the acceptor substrate specificity of the FTs by thin-layer chromatography indicated that both caput and cauda sperm expressed alpha(1-2)-, alpha(1-3)-, alpha(1-4)-FTs as demonstrated by fucose incorporation into phenyl-beta-D-galactoside, 2'-fucosyllactose, and lacto-N-fucopentaose-I, respectively. Spermatozoa from the cauda epididymidis exhibited significant decreases in the levels of alpha(1-2)-, alpha(1-3)-, alpha(1-4)-FTs, and of total soluble FTs in comparison to spermatozoa from the caput epididymidis. The relative ratio of alpha(1-3)-FT to total FT activity appeared to be significantly higher than those of alpha(1-2)- or alpha(1-4)-FTs, in spermatozoa both from caput and cauda epididymides. Using different types of low molecular weight acceptors and the selective inhibition of the FT by N- ethylmaleimide, we have demonstrated that at least alpha(1-2)-FT is different from alpha(1-3)- or alpha(1-4)-FTs. Kinetic studies also showed that alpha(1-2)-FT is different from alpha(1-3)- or alpha(1-4)-FTs as demonstrated by apparent Km and Vmax values. Moreover, alpha(1-3)- and alpha(1-4)-FT activities in cauda sperm were found to be highly sensitive to Mn2+ but showed differential responses to divalent cations. In contrast, both alpha(1-3)- and alpha(1-4)-FTs seemed to be relatively less sensitive to Mg2+. Thus, these results not only demonstrate the presence of multiple FTs in rat epididymal sperm but also differentiate individual FTs with regard to their kinetic properties and sensitivity to both inhibitor and divalent cations.
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PMID:Glycosidic specificity of fucosyltransferases present in rat epididymal spermatozoa. 857 85

When the plasma membranes of caput and cauda epididymal spermatozoa of hamster were evaluated for their ability to undergo phosphorylation, a differential phosphorylation of the membrane proteins was observed. In the plasma membranes of the caput epididymal spermatozoa (immature), twelve proteins were phosphorylated (100, 76, 67, 65, 55, 52, 47, 42, 38, 32, 30, and 20 kD), whereas in the plasma membranes of cauda epididymal spermatozoa (mature), a differential phosphorylation pattern was observed with respect to the 94, 67, 52, and 47 kD proteins. The 94 kD protein was found to be phosphorylated and the 67 kD protein was found to be not phosphorylated in cauda spermatozoal plasma membrane (Cd SPM) in contrast to this protein in caput spermatozoal plasma membrane (Cpt SPM). The 52 and 47 kD proteins were also more intensely phosphorylated in Cd SPM than Cpt SPM. The 100 kilodalton protein, although present in both Cpt and Cd sperm plasma membranes, was found to be phosphorylated at the tyrosine residues only in the Cd SPM, as indicated by the Western blot using antiphosphotyrosine antibody. Further, a differential phosphorylation of the substrate proteins present in the Cpt and Cd SPM was seen when Mg2+ in the assay buffer was replaced by other divalent cations. For instance, Zn2+ stimulated the phosphorylation of an 85 kD protein in cauda SPM and not in the caput SPM and Ca2+ stimulated the phosphorylation of a 76 kD protein only in the cauda SPM. The phosphoproteins in both the plasma membranes were found to be phosphorylated predominantly at the tyrosine residue. The differential phosphorylation at a 100 kD protein at tyrosine in the Cd SPM (Western blot), which is absent in the immature Cpt SPM, also indicated that certain proteins in the hamster spermatozoa are phosphorylated in a maturation-specific manner.
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PMID:A maturation-related differential phosphorylation of the plasma membrane proteins of the epididymal spermatozoa of the hamster by endogenous protein kinases. 917 Jan 14

The activity of alpha 3-D-mannoside-beta-1,2-N-acetylglucosaminyltransferase I (GnT I; EC 2.4.1.101), which catalyzes the first step in the conversion of oligomannose to complex or hybrid N-glycans of glycoproteins, was detected in rat testicular and cauda epididymal fluids. The GnT I activity of testicular fluid had a pH optimum of 6.0, whereas that of the cauda epididymal fluid was optimal at pH 7.0. The enzyme in testicular fluid had an absolute requirement for either Co2+, or Mn2+, Mg2+ and Ca2+, the activity being stimulated by these cations in the above order, whereas that of cauda epididymal fluid had an absolute requirement for Mn2+ or Ca2+, with Co2+ and Mg2+ being ineffective. The specific activity of GnT I in cauda epididymal fluid was somewhat higher than in testicular fluid. The apparent Km value for alpha 1-3 alpha 1-6mannopentaose of GnT I in the testicular and epididymal fluids was 0.57 and 0.38 mM, respectively. The substrate specificity for both GnT I activities decreased in the following order: alpha1-3 alpha 1-6mannopentaose>alpha1-3 alpha 1-6mannotriose>alpha 1-3mannobiose>alpha 1-6mannobiose. These data suggest that two forms of GnT I exist in the testicular and epididymal fluids.
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PMID:Are there two forms of beta 2-N-acetylglucosaminyltransferase I in rat testicular and epididymal fluids? 1287 32

Early investigators reported the occurrence of unidentified protein factors in biological fluids that may regulate sperm motility essential for fertility potential. This study reports for the first time purification of a forward motility stimulating protein (FMSF-I), to apparent homogeneity, from a biological fluid (buffalo blood serum) and its characterization. FMSF-I is the major motility protein of buffalo serum: a rich source of the factor. FMSF showed high protein specificity and affinity for activating forward motility of goat cauda epididymal spermatozoa. The motility promoter at 0.5 microM level showed maximal activity when nearly 60%-70% of spermatozoa expressed forward motility. It is a 66 kDa monomeric acidic protein rich in aspartate, glutamate, and leucine with isoelectric point of 3.7. FMSF: a Mg2+ -dependent protein binds to concanavalin A-agarose and the glycoprotein nature of FMSF has been confirmed by PAS staining. The factor lost activity completely when treated with alpha-mannosidase showing that the sugar part of the protein is essential for its biological activity. FMSF has no species specificity for its motility-activating potential. Sperm surface has specific receptors of FMSF, which is strongly immunogenic. The factor is present in testis and epididymis although liver is its richest source. Motility promoting efficacy of FMSF is markedly higher than the well-known non-protein motility activators: theophylline and bicarbonate or their combination. FMSF is a physiological activator of sperm motility and as a slaughterhouse byproduct it has potentiality for solving some of the problems of animal breeding, conservation of endangered species, and human infertility: a global social problem.
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PMID:Identification and characterization of a sperm motility promoting glycoprotein from buffalo blood serum. 1688 95

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