Acrosome reaction

The acrosome reaction is an important step in the generation that enables the sperm to penetrate the ovum.

Primary binding of the sperm cell

Must be said that, that the egg with the zona pellucida has a protective shell that also plays an essential role in fertilization. The "first contact" a capacitated sperm with this protective cover is referred to as primary or initial bond between egg and sperm cell. In these encounter Contact proteins on the surface of the sperm cell and the protein ZP3 of the zona pellucida, the acrosome reaction which triggers.

This merges the cell membrane of the sperm in the head region with the membrane of the acrosome, a component of the sperm cell. The hydrolyzing enzymes contained in the acrosome are released with it, and as a direct result of the zona pellucida is dissolved at this point ( lysed ). The cell membrane is lost at the tip of the sperm head. Before the core of the sperm is now only the inner ( rear ) membrane of the acrosome.

Secondary binding of the sperm cell

The secondary binding of sperm is now on the zona pellucida protein ZP2, whereby both the maintenance and enhancement of binding are possible.

An acrosome reaction is only possible with fully capacitated sperm. Thus, the acrosome reaction can be used as the most important summary parameters for male fertility: Is the ability to move ( motility ) of the sperm disturbed, they do not reach the fallopian tubes. Achieve this well, there is here, however, problems with the capacitation, acrosome reaction which is inhibited. Accordingly, the acrosome reaction is considered to be also applicable in a laboratory test to assess the fertilizing capacity of the sperm.

• Reproductive Medicine