Isolation of two novel E prostaglandins in human seminal fluid

cis-8,11,14,17-[1-14C]Eicosatetraenoic acid was incubated with microsomes of ram seminal vesicles and 1 mM glutathione for 3 min at 37 degrees C. The main metabolite was identified as 17,18-dehydroprostaglandin E1 by capillary column gas chromatography-mass spectrometry. Human seminal fluid was analyzed for the presence of 17,18-dehydroprostaglandin E1 and prostaglandin E3. Whereas prostaglandin E3 could be demonstrated by capillary gas chromatography-mass spectrometry, 17,18-dehydroprostaglandin E1 could not be found under these conditions. However, human seminal fluid contained two compounds with a similar polarity on reversed phase high performance liquid chromatography as 17,18-dehydroprostaglandin E1 and prostaglandin E3. The two compounds were identified as 18,19-dehydroprostaglandin E1 and 18,19-dehydroprostaglandin E2 by gas chromatography-mass spectrometry, by UV analysis after conversion to the corresponding prostaglandin B compounds, and by ozonolysis. The amount of each of the two prostaglandins in human seminal fluid seemed to be in the same order of magnitude as the amount of prostaglandin E3.     

Kininase II from human seminal plasma. Isolation and properties

A rapid and highly efficient procedure for purification of kininase II from human seminal plasma is described. After ultra centrifugation, the enzyme was purified by gel filtration on Sepharose 6B CL and ion exchange chromatography followed by affinity chromatography of EDTA-inhibited enzyme on bradykinin-Sepharose. The enzyme was specifically inhibited by Captopril and BPP9a but not by phosphoramidon. PAGE in the presence of sodium dodecyl sulfate under reducing conditions resulted in two major protein bands with apparent molecular masses of about 55 kDa and 65 kDa and two faint protein bands at higher molecular masses. Antibodies raised against the major protein bands showed full cross reactivity with all four protein bands. The presented data indicate that kininase II consists of subunits.     

Involvement of semenogelin-derived peptides in the antibacterial activity of human seminal plasma

Mechanisms for protecting spermatozoa, and the testes that produce them, from infection are essential, given the importance of these cells and organs for the fertility of the individual and perpetuation of the species. This is borne out by the publication of numerous papers on this subject over the last 50 years. We extended our work and that of others on the anti-infectious defense system of the male genital tract, using a new strategy for the direct identification of antibacterial molecules in human seminal plasma. We subjected a liquefied seminal plasma cationic fraction to reversed-phase HPLC, monitored microbicidal activity by gel overlay and radial diffusion assays, and identified the proteins and/or peptides present in each active fraction by mass spectrometry. In addition to proteins with known potent microbicidal activity--phospholipase A2, lactoferrin, and lysozyme--we also found that peptides produced by cleavage of semenogelin I, the predominant human semen coagulum protein, had high levels of antibacterial activity.     

Detection of prostatic tissue and seminal plasma peptides reacting with human seminal fluid acid phosphatase antibodies

IgG1 monoclonal antibody to purified seminal fluid phosphatase was raised by fusion of spleen cells from immunized mice with cell line Sp2/O-Ag 14 using simple method of screening for antiphosphatase antibody secreting clones. All molecular forms of catalytically active seminal fluid phosphatase and prostatic tissue phosphatase, resolved by chromatofocusing in pH gradient, react with this monoclonal antibody and with rabbit antiserum to purified seminal fluid phosphatase. Peptides of Mr 25,000 to 76,000 and of Mr 13,000 to 76,000 were adsorbed from the prostatic tissue extract and from seminal plasma on the monoclonal antibody-Sepharose column.     

Isolation and characterization of a basic carboxypeptidase from human seminal plasma

A carboxypeptidase which cleaves the C-terminal arginine or lysine from peptides was purified by a two-step procedure; gel filtration on Sephacryl S-300 and affinity chromatography on arginine-Sepharose. The activity increased 280% after the first step, indicating the removal of an inhibitor from the crude starting material. The activity in the crude seminal plasma eluted from the Sephacryl S-300 column with an apparent Mr 98,000 and after purification with an Mr 67,000, indicating that it binds to another protein in the crude seminal plasma. When analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, a single band at Mr 53,000 was seen which was converted to two smaller bands (Mr 32,000 and/or 26,000) after reduction. The seminal plasma carboxypeptidase has a neutral pH optimum, is inhibited by o-phenanthroline and by the inhibitor of carboxypeptidase B-type enzymes, 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid, and can be activated by cobalt. The purified enzyme has a high specific activity (67.8 mumol/min/mg) with the ester substrate benzoyl (Bz)-Gly-argininic acid and readily cleaves Bz-Ala-Lys, Bz-Gly-Arg, and Bz-Gly-Lys. It also hydrolyzes biologically active peptides such as bradykinin (Km = 6 microM, kcat = 43 min-1), Arg6-Met5-enkephalin (Km = 103 microM, kcat = 438 min-1), and Lys6-Met5-enkephalin (Km = 848 microM, kcat = 449 min-1). The seminal plasma carboxypeptidase did not cross-react with antiserum to human plasma carboxypeptidase N; other properties distinguish it from the blood plasma enzyme as well as from pancreatic carboxypeptidase B and granular, acid carboxypeptidase H (enkephalin convertase). The carboxypeptidase could be involved in the control of fertility by activating or inactivating peptide hormones in the seminal plasma. In addition it could contribute to the degradation of basic proteins during semen liquefaction.     

Isolation of a new actin-binding protein from human seminal plasma

Interaction of a protein of human seminal plasma with actin was detected by agar gel immunoelectrophoresis. A major actin-binding protein was isolated from human seminal plasma using an actin-Sepharose 4B column followed by fast-performance liquid chromatography with an anion-exchange Mono-Q column. The protein showed a single band under reduced conditions on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in a position corresponding to a molecular mass of 20 kDa. This 20 kDa polypeptide was detected in saliva and extracts of the submandibular gland and seminal vesicles as well as seminal plasma by the method of immunoblotting using monospecific antibody against the 20 kDa antigenic component of human seminal plasma. The protein might be called secretory actin-binding protein (SABP).     

Study of peptides inhibiting the angiotensin-converting enzyme of human seminal plasma.

Several peptides were investigated for their inhibitory capacity against dipeptidyl carboxypeptidase (angiotensin-converting enzyme) from human seminal fluid. The strongest inhibitor was the nonapeptide SQ 20881. A marked inhibition was also shown by the compounds Phe-Ala-Pro and Boc-Phe-Ala-Pro, which behaved as competitive inhibitors. Among the peptides related to angiotensin, angiotensin III was the strongest inhibitor, followed by angiotensin II and the C-terminal hexapeptide of angiotensin II. The results indicate the dipeptidyl carboxypeptidase of human semen is very similar to pulmonary dipeptidyl carboxypeptidase in its susceptibility to peptide inhibitors. In view of these and other previously reported similarities, it is possible that both enzymes are identical.     

Isolation and immunological determination of retinol-binding protein in human plasma

A retinol-binding protein and prealbumin both in the homogeneous state are isolated from human blood serum. Immunization of rabbits is used to obtain antibodies against the retinol-binding protein; the highly specific method is developed for quantitative determination of the content of retinol-binding protein in human blood. The method may be widely applied in the biochemical and clinical practice.     

Isolation and characterization of the major form of beta-glucuronidase from human seminal plasma

Human seminal plasma contain two forms of beta-glucuronidase (beta-D-glucuronidase glucuronosohydrolase, EC 3.2.1.31) which are present in the ratio of 4:1. The major form of beta-glucuronidase with a slow moving band in electrophoresis was purified to homogeneity as revealed by polyacrylamide gel electrophoresis, double immunodiffusion and immunoelectrophoresis. The major form of beta-glucuronidase shows dual optimum pH at 4.3 and 4.7 with a dip in the activity at pH 4.5. The Km of this form of beta-glucuronidase is dependent on pH and was found to be 0.95, 3.08 and 0.67 mM at pH 4.4, 4.5 and 4.7, respectively. The major form of beta-glucuronidase from seminal plasma is stable at 55 degrees C for 30 min but it denatures at 65 degrees C. Heat denaturation is faster at acidic pH (4.7) than at alkaline pH (7.8). However, the activity of enzyme increased linearly with increase in temperature up to 70 degrees C during incubation with substrate. Cu, Ag, Hg and Ni salts inhibited enzyme activity significantly at 0.1 and 1.0 mM concentration, but the inhibition of HgCl2 was protected by cysteine. 1,4-D-Saccharic acid lactone and ascorbic acid inhibited seminal beta-glucuronidase competitively, yielding Ki values of 1.7 . 10(-3) mM and 10.3 mM, respectively. Though fructose and mannose also showed significant inhibition of beta-glucuronidase at 10-100 mM, glucose did not show any effect. The molecular weight of the major form of beta-glucuronidase was found to be 279 000, and it appears to be composed of four subunits each having a molecular weight of 74 000.     

Isolation and identification of two neutral thyrotropin releasing hormone-like peptides, pyroglutamylphenylalanineproline amide and pyroglutamylglutamineproline amide, from human seminal fluid.

Two tripeptide amides with stuctures similar to thyrotropin releasing hormone were isolated from human seminal fluid and their amino acid sequences determined. The peptides were purified by gel exclusion from Sephadex G50 and were detected by radioimmunoassay with thyrotropin releasing hormone antibody; in addition, N-terminally extended forms were demonstrated by radioimmunoassay after trypsin digestion. Further purification of the tripeptides was by chromatography on SP-Sephadex C25 and by high performance liquid chromatography on C18 Microbondapak using an HCl/acetonitrile gradient. After exclusion from mini-columns of SP-Sephadex C25 and DEAE-Sephadex A25, two neutral peptides were obtained in homogeneous form by high performance liquid chromatography with an HCl/methanol gradient. Amino acid analysis gave the following compositions: Glu, 0.74, Phe, 1.0, Pro, 1.0; and Glu, 1.72, Pro, 1.0. Both peptides possessed a blocked N terminus, but after opening the pyroglutamyl ring the sequences Glu-Phe-Pro and Glu-Glx-Pro were demonstrated. The chromatographic properties of the endogenous peptides were identical to the properties of the corresponding synthetic peptides. The structure of pGlu-Phe-Pro (where p-indicates pyro-) amide was confirmed by fast atom bombardment mass spectrometry. The presence in human semen of three structurally related peptides, pGlu-Phe-Pro amide, pGlu-Gln-Pro amide, and the previously reported pGlu-Glu-Pro amide (Cockle, S. M., Aitken, A., Beg, F., and Smyth, D. G. (1989) J. Biol. Chem. 264, 7788-7791), suggests that this series of peptides may have evolved to fulfil complementary biological roles.     

HIV-1 enhancing effect of prostatic acid phosphatase peptides is reduced in human seminal plasma

We recently reported that HIV-1 infection can be inhibited by innate antimicrobial components of human seminal plasma (SP). Conversely, naturally occurring peptidic fragments from the SP-derived prostatic acid phosphatase (PAP) have been reported to form amyloid fibrils called "SEVI" and enhance HIV-1 infection in vitro. In order to understand the biological consequence of this proviral effect, we extended these studies in the presence of human SP. PAP-derived peptides were agitated to form SEVI and incubated in the presence or absence of SP. While PAP-derived peptides and SEVI alone were proviral, the presence of 1% SP ablated their proviral activity in several different anti-HIV-1 assays. The anti-HIV-1 activity of SP was concentration dependent and was reduced following filtration. Supraphysiological concentrations of PAP peptides and SEVI incubated with diluted SP were degraded within hours, with SP exhibiting proteolytic activity at dilutions as high as 1:200. Sub-physiological concentrations of two prominent proteases of SP, prostate-specific antigen (PSA) and matriptase, could degrade physiological and supraphysiological concentrations of PAP peptides and SEVI. While human SP is a complex biological fluid, containing both antiviral and proviral factors, our results suggest that PAP peptides and SEVI may be subject to naturally occurring proteolytic components capable of reducing their proviral activity.     

Primary structure of a new actin-binding protein from human seminal plasma

Secretory actin-binding protein (SABP), a glycoprotein from human seminal plasma, was isolated according to Akiyama and Kimura [Akiyama, K. & Kimura, H. (1990) Biochim. Biophys. Acta 1040, 206-210]. The complete amino acid sequence of SABP was determined with the aid of fragments generated by trypsin, Staphylococcus aureus V8 protease and pepsin. The single polypeptide chain of SABP contains 118 amino acids with a calculated Mr of 13,506 and pyroglutamic acid as the N-terminal residue. A single N-glycosidic carbohydrate moiety is located at Asn77. The carbohydrate composition shows an unusually high amount of fucose. The arrangement of the two disulfide bonds is Cys37-Cys63 and Cys61-Cys95. Sequence comparison revealed a high degree of similarity with a 14-kDa submandibular gland protein from mouse (45% identity and 64% similarity). SABP is identical with a prolactin-inducible protein and a protein termed gross cystic disease fluid protein 15 (sequences translated from cDNA clones), both from human breast tissues. Although SABP was also detected in saliva, in extracts of the submandibular gland and seminal vesicles, little is known of its function.     

Development and validation of a sensitive radioimmunoassay for naturally occurring beta-endorphin-like peptides in human plasma

β-Endorphin-like peptides in blood plasma of normal human subjects were studied by means of a radioimmunoassay (RIA) and gel filtration. Plasma was extracted with silica gel, which was washed with water and 1 n HCl, and eluted with 50% acetone. Plasma extracts thus obtained and standard synthetic human β-endorphin yielded parallel RIA curves. Total immunoreactivity in normal donors ranged from 1.2 to 10.4 fmol/ml (21 subjects). The immunoreactivity was completely destroyed by treatment with papain. Gel filtration indicated the presence of three components-one of unknown nature at the void volume and the others at elution positions characteristic of β-lipotropin and β-endorphin. Recoveries of human β-endorphin and β-lipotropin added to plasma were 53 and 58%, respectively. Addition of N-ethylmaleimide to plasma or of aprotinin to blood immmediately following collection had no effect on the amount of total immunoreactivity. Furthermore, a large amount of β-endorphin-like immunoreactivity. The above results lead us to conclude that a β-endorphin-like immunoreactive peptide occurs naturally in plasma of normal human subjects.     

Lucigenin chemiluminescence in human seminal plasma

Seminal plasma protects spermatozoa from the detrimental effects of reactive oxygen species such as hydrogen peroxide. We investigated the lucigenin-dependent chemiluminescence in cell-free seminal plasma from andrological patients. The seminal plasma was separated from cells by centrifugation. In all seminal plasmas studied lucigenin-dependent chemiluminescence (LCL) was detected. The LCL showed a strong pH-dependence. The signal was stable if samples were stored at +4°C for up to 4 days or up to 8 days at -80°C. Filtration of the samples (0.45 and 0.22 μm pore size) did not lower their luminescence. The addition of superoxide dismutase (SOD) and ascorbic acid oxidase (AAO) lowered LCL nearly to baseline values while trolox and desferal showed moderate effect, whereas allopurinol had no effect. Electron paramagnetic resonance spectroscopy demonstrated ascorbyl radicals in seminal plasma. Physiological concentrations of ascorbic acid yielded SOD-inhibitable lucigenin-chemiluminescence. The nitroblue-tetrazolium assay showed that ascorbic acid in buffer solution produced formazan. Superoxide-anion radicals were not detected in seminal plasma by the spin-trap DEPMPO due to their low steady state concentration. It is concluded that in seminal plasma ascorbate reacts with molecular oxygen yielding ascorbyl radicals and superoxide anion. If lucigenin is added to seminal plasma, reducing substances present, such as ascorbate, reduce lucigenin to the corresponding radical; this radical reacts with molecular oxygen and also forms O₂^-2. So LCL in human seminal plasma results from the autoxidation of ascorbate and the oxidation of the reduced lucigenin. While the physiological relevance of the former mechanism is unknown, the latter is an artifact.     

Fibronectin fragments in human seminal plasma

The study has revealed the presence of fibronectin (FN) fragments and a lack of intact FN in 72 seminal plasma samples. The FN fragmentation was examined by immunoblotting with a monoclonal antibody specific to the central cellular FN domain and was confirmed with a monoclonal antibody directed to the C-terminal domain of FN. Nine FN fragments between 60 and 200 kDa and five fragments of 60-150 kDa were identified in seminal plasma samples of normozoospermic and of terato-, oligoterato-, and oligoasthenoterato-spermic groups, respectively. The relative amounts of the 60, 90 and 100 kDa FN fragments were 2-3 times higher in seminal plasmas with abnormal semen characteristics than in the normozoospermic group. The results suggest that seminal plasma FN fragments may contribute to fertilization and the analysis of FN fragmentation may have a diagnostic value in andrological investigations.