Acrosin (an enzyme that acts as a protease) and Hyaluronidase

In Eutherian mammals the acrosome contains digestive enzymes (including hyaluronidase and acrosin).

The spem head or acrosome cap contains digestive enzymes such as hyaluronidase and acrosin which are used to lyse the outer wall of the ovum during fertilization

So that the sperm can break through to fertalise the egg.
Because it enters to egg cell through its head only. The enzymes present at the top of its head facilitate the penetration of sperm in the egg cell.

An acrsome is an organelle that develops over the anterior half of the sperm's head. Its purpose is to break down the outer layer of the ovum so the sperm can join the egg.