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Once the sperm enters into the female reproductive tract, they undergo an important process called capacitation, which involves a series of physiological and biochemical changes that ensure fertilization. During capacitation, calcium ions (Ca2+) increase the bending amplitude of a sperm’s flagellum. This causes hyperactivation, which is manifested as the asymmetrical beating of the flagellum. Tyrosine phosphorylation is also a cause for human sperm hyperactivation; asthenospermia—that is, reduced sperm motility—occurs when the sperm are incapable of hyperactivation owing to impaired tyrosine phosphorylation.[1] Hyperactivated motility enables the sperm to migrate and penetrate the cumulus cells and zona pellucida surrounding the oocyte, leading to fertilization. Therefore, the hyperactivated motility of sperm is critical for male reproductive ability, and the molecular mechanism underlying human sperm …