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Sperm acrosome membrane-associated protein 1 SPACA1 (aka SAMP32, due to its 32kDa M.W.) is localized to the acrosome of spermatozoa. The acrosome is an organelle transformed from the Golgi apparatus to form a cap over the anterior portion of the spermatozoa head, which contains the sperm nucleus. Mammalian acrosomes contain digestive enzymes that degrade the ovum outer membrane (zona pellucida) to allow fusion of the sperm and ovum nuclei via the acrosomal reaction. In mammals, the acrosome releases hyaluronidase and acrosin. Antibodies generated against recombinant SPACA1 have been shown to inhibit human sperm binding and membrane fusion in vitro vs. zona-free hamster ova. Male mice lacking SPACA1 are infertile, and exhibit globozoospermia-like misformed sperm heads. SPACA1 content has been reported to be diminished in a comparison of round-headed vs normal spermatozoa. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",