Characterization of acid and neutral alpha-mannosidases in bull semen and reproductive organs

Non-targeted proteomic analysis of Asian elephant (Elephas maximus) seminal plasma using an in-solution digestion technique and liquid chromatography tandem-mass spectrometry

Seminal plasma proteins have recently been reported to play a significant role as valuable materials for understanding male reproductive biology, identifying causes of fertility problems, and developing reproductive biomarkers. Proteomic analysis of seminal plasma holds promise in advancing the understanding of male Asian elephant reproductive biology. This study aims to explore seminal plasma proteins of Asian elephants and their probable functions to provide fundamental information about male reproduction in this species. The protein solution from pooled seminal plasma from 10 bulls (a total of 33 ejaculates) was digested into peptides and identified using LC-MS/MS. Out of 986 proteins, 597 were mapped and matched with 58 species in UniProt databases, including Elephas maximus. These mapped proteins were mostly involved in binding function, catalytic activity, cellular process, and metabolic process. Only 29 mapped proteins were recognized to be related in reproductive process, mainly associated in spermatogenesis and sperm capacitation. Additionally, several seminal plasma proteins related to fertility or semen quality in other mammals were also found in Asian elephant semen, such as keratin type I, aldose reductase, thrombospondon-1, fibronectin 1, platelet-activating factor acetyl hydrolase, mannosidase, and semenogelin-2. This discovery clearly reveals the beneficial protein profile in seminal plasma of the Asian elephant and serves as a crucial step in investigating infertility and poor semen quality in this valuable species.

Acid glycosidases from hen oviduct and egg albumen

Activities of seven acid glycosidases: beta-N-acetylhexosaminidase (beta-HEX), alpha- and beta-galactosidase (alpha- and beta-GAL), alpha- and beta-mannosidase (alpha- and beta-MAN), alpha-glucosidase and alpha-fucosidase in magnum region of hen (Gallus gallus domesticus) oviduct, and four acid glycosidases: beta-HEX, beta-GAL, alpha- and beta-MAN in egg albumen, were investigated. beta-HEX from magnum and egg albumen hydrolysed 4-methylumbelliferyl-beta-N-acetylhexosamine-6-sulphate (4-MeUmbGlcNAc-6-SO(4)) like mammalian beta-HEX form A. Multiple forms of magnum and egg albumen beta-HEX, beta-GAL, alpha- and beta-MAN were separated by strong anion exchange chromatography and chromatofocusing method. Chromatofocusing of the magnum resulted in the appearance of multiple forms for beta-HEX with pI of 6.18, 5.43, 5.55, 5.34, 5.27 and 5.16, for beta-GAL with pI of 4.98, 4.84, 4.77, 4.64 and 4.68-4.63, for alpha-MAN with pI of >or=7.4, 6.75, 6.62 and 6.26, and for beta-MAN two forms with pI of 6.37 and 5.77. Chromatofocusing of egg albumen yields multiple forms for beta-HEX with pI of 6.24, 6.08, 5.55 and 5.35, for beta-GAL two forms with pI of 5.10 and 4.86-4.80 for alpha-MAN multiple forms with pI of >or=7.4, 6.80, 6.60 and 6.30, and for beta-MAN forms with pI of 6.30 and 5.77. In conclusion, this study was the first to show beta-HEX activity against 4-MeUmbGlcNAc-6-SO(4) in the magnum and albumen of bird eggs, corresponding to beta-HEX A activity in mammals. Main multiple forms of beta-HEX, beta-GAL, alpha- and beta-MAN occurring in the magnum were revealed in the egg albumen. Comparison with a cock of the same breed showed that hen egg magnum and albumen has the same multiple forms of the enzymes that are found in the epididymides and seminal plasma of the cock.

Novel alpha-D-mannosidase of rat sperm plasma membranes: characterization and potential role in sperm-egg interactions

During the course of a study of glycoprotein processing mannosidases in the rat epididymis, we have made an intriguing discovery regarding the presence of a novel alpha-D-mannosidase on the rat sperm plasma membranes. Unlike the sperm acrosomal "acid" mannosidase which has a pH optimum of 4.4, the newly discovered alpha-D-mannosidase has a pH optimum of 6.2, and 6.5 when assayed in sperm plasma membranes and intact spermatozoa, respectively. In addition, the two enzymes show different substrate specificity. The acrosomal alpha-D-mannosidase is active mainly towards synthetic substrate, p-nitrophenyl alpha-D-mannopyranoside, whereas the sperm plasma membrane alpha-D-mannosidase shows activity mainly towards mannose-containing oligosaccharides. Evidence is presented which suggest that the sperm plasma membrane alpha-D-mannosidase is different from several processing mannosidases previously characterized from the rat liver. The newly discovered alpha-D-mannosidase appears to be an intrinsic plasma membrane component, since washing of the purified membranes with buffered 0.4 M NaCl did not release the enzyme in soluble form. The enzyme requires nonionic detergent (Triton X-100) for complete solubilization. The enzyme is activated by Co2+ and Mn2+. However, Cu2+ and Zn2+ are potent inhibitors of the sperm plasma membrane alpha-D-mannosidase. At a concentration of 0.1 mM, these divalent cations caused nearly complete inactivation of the sperm enzyme. In addition methyl-alpha-D-mannoside, methyl-alpha-D-glucoside, mannose, 2-deoxy-D-glucose, and D-mannosamine are inhibitors of the sperm surface alpha-D-mannosidase. The physiological role of the newly discovered enzyme is not yet known. Several published reports in three species, including the rat, suggest that the sperm surface alpha-D-mannosidase may have a role in binding to mannose-containing saccharides presumably present on the zona pellucida.

Comparison of glycosidase levels in bovine seminal plasma

Seven glycosidases (beta-N-acetylglucosaminidase, alpha-fucosidase, beta-galactosidase, acid alpha-glucosidase, beta-glucuronidase, acid and neutral alpha-mannosidase) were analysed in seminal plasma from the first and second successive ejaculates in normal Ayrshire bulls. In comparison to our previous data the results indicate that beta-N-acetylglucosaminidase, beta-galactosidase and beta-glucuronidase are derived mainly from epididymal secretions, while alpha-fucosidase and particularly neutral alpha-mannosidase originate additionally from the spermatozoan cytoplasmic droplets. The seminal vesicles appear to contribute particularly to the seminal plasma acid alpha-glucosidase and acid alpha-mannosidase activities. The seminal plasma enzymes derived from the epididymis and cytoplasmic droplets were suppressed in semen samples with low sperm density or with high numbers of abnormal spermatozoa. The epididymal and seminal vesicle enzymes could be utilized in assessment of the secretory/functional capacity of these glands.