Crypticity and functional distribution of the membrane associated α-L-fucosidase of human sperm

• Published in: Molecular reproduction and development 2007-06, Vol.74 (6), p.758-766
• Main Authors: Venditti, Jennifer J., Donigan, Katherine A., Bean, Barry S.
• Format: Article
• Language: English
• Subjects: acrosome; Acrosome - metabolism; Adolescent; Adult; alpha-L-Fucosidase - metabolism; Binding Sites; Biological and medical sciences; Cell Membrane - metabolism; DFJ; equatorial segment; fertilization; fucose; Fucose - metabolism; Fundamental and applied biological sciences. Psychology; gamete; Hormone metabolism and regulation; Humans; Male; Mammalian male genital system; Protein Binding; Sperm Capacitation - physiology; Spermatozoa - enzymology; Spermatozoa - metabolism; Tissue Distribution; Vertebrates: reproduction
• ISSN: 1040-452X; 1098-2795
• DOI: 10.1002/mrd.20666

Two distinctive isoforms of the enzyme α‐L‐fucosidase are found within human semen in substantial amounts, suggesting specialized functions during reproduction. The membrane‐associated isozyme of human sperm cells was previously characterized biochemically, and here we report on its subcellular localization. Intact, detergent permeabilized, capacitated, and acrosome‐reacted sperm were investigated using antifucosidase immunofluorescence, binding of the fluorescent fucosylated glycoconjugate RITC‐BSA‐fucose (RBF), and enzyme activity in the presence and absence of selected inhibitors. Both immunolocalization and RBF binding show that fucosidase is broadly distributed over the membrane systems of human sperm, but is relatively enriched within the equatorial segment. Upon detergent treatment or induction of acrosome reaction (AR), a portion of enzyme activity is recoverable in the supernatant, presumably associated with released remnants of the outer acrosomal membrane. Surprisingly, cell‐bound enzyme activity increases sharply following permeabilization of intact sperm, representing cryptic fucosidase that is relatively stable and corresponds with strong fluorescence in the equatorial segment and other sperm membranes. These observations support the notion that the fucosidase has a role in the intimate species signature interactions between sperm and oocyte. Mol. Reprod. Dev. 74: 758–766, 2007. © 2006 Wiley‐Liss, Inc.