What is "capacitation"

n. 1 enablement. 2 (context zoology English) The process of altering sperm to allow them to fertilize eggs.

Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation. In vivo this step typically occurs after ejaculation, in the female reproductive tract. In vitro, capacitation can occur by incubating sperms that have either undergone ejaculation or have been extracted from the epididymis in a defined medium for several hours.

The uterus aids in the steps of capacitation by secreting sterol-binding albumin, lipoproteins, proteolytic and glycosidasic enzymes such as heparin.

Non-mammalian spermatozoa do not require this capacitation step and are ready to fertilize an oocyte immediately after release from the male. After this capacitation the sperm must undergo activation involving the acrosome reaction.