1). In the sperm-peak portion (first fraction), where most spermatozoa are present, other proteins, presumably of epididymal origin,

such as Lipocalins and inhibitor of acrosin/trypsin, are detected.6 In other species, find more such as the stallion, protein amounts follow a similar disposition and main SP proteins are equivalent: Fn-2, CRISPs and spermadhesins. These proteins, initially described as horse seminal protein (HSP)-1 to HSP-8, are mostly of low molecular weight (14–30 kDa) forming multi-protein aggregates, which – with the exception of HSP-4 – attach to the sperm surface.41 The two major proteins, the heparin-binding HSP-1 and HSP-2, accounted for 70–80% of the total protein and were considered modulators of capacitation. Both HSP-1 and HSP-2 (also called SP-1 and SP-2) are short Fn-2 type proteins, similar to the major bovine heparin-binding proteins (BSP), also associated with capacitation.42 These Fn-2 type proteins bind to phosphatidylcholine or sphingomyelin phospholipids of the ejaculated sperm membrane, causing changes in the membrane structure.43,44 The HSP-3 (or equine CRISP-3) is associated with fertility45 perhaps via its role as selective protector against PMN cell selleck screening library binding.46 Examining fractions of the equine ejaculate, the first fractions contained

acrosine inhibitor and PSA or kallikrein-like proteins (as HSP-6 and HSP-8 representing isoforms), yet with all HSPs being present Acyl CoA dehydrogenase in the rest of the fractions and HSP-1 being the major protein present in all ejaculate fractions.47 HSP-7 is the only member of the spermadhesin family, and like its porcine homologue AWN-1, shows ZP-binding activity.48 Human SP is also a rich source of proteins and phosphatases, aminopeptidases, glycosidases, hyaluronidase, mucin, etc. been detected more than 50 years ago.15 Since then, more and more spots have been identified, and SP proteins corresponding

to the same parent protein appear in multiple spots and bands, implying that there is a clear multiplicity of isoforms present, independently of the SP source (expressed prostate49,50) or the bulk ejaculate.51 Thousands of unique proteins have over time been identified, of which ∼25% were secretory.52,53 The major accessory glands of men contribute differentially to the SP protein pool. The major protein constituents of the seminal vesicle fluid are mainly semenogelin I but also semenogelin II, involved in the gelification of the latter spurts of the ejaculate (coagulum) and, following liquefaction, yielding products with clear biological functions such as inhibition of sperm motility, antibacterial activity, etc. alongside with other seminal vesicle proteins that include lactoferrin, fibronectin and protein C-inhibitor.