The enzyme responsible for unzipping the DNA helix during DNA replication is DNA helicase.

Here's how it works:

1. Binding: DNA helicase binds to the DNA molecule at the origin of replication.

2. Unwinding: It then uses energy from ATP hydrolysis to break the hydrogen bonds between the nitrogenous bases of the two DNA strands.

3. Separation: This process separates the strands, creating a replication fork with two single-stranded DNA templates.

This unwinding process is crucial for DNA replication, allowing each strand to serve as a template for the synthesis of a new complementary strand.