Probable component of sperm glycocalyx. Likely protects and facilitates transport of sperm in the female reproductive tract. Probably released from the sperm surface during capacitation. In the corpus epididymis, located in vesicles below the apical surface of the plasma membrane. Secreted by epididymal cells and absorbed to the surface of sperm during transit through the epididymis. Coats the entire surface of ejaculated sperm although presence on the equatorial segment is less intense. Specifically expressed in corpus epididymis and cauda epididymis with expression in corpus being highest (at protein level). Not detected in other tissues tested, including testis, prostate, seminal vesicle and vas deferens (at protein level). O-glycosylated; glycans contain alpha(2,3)-linked sialic acids. Belongs to the beta-defensin family.