Is when an enzyme changes shape. once this happens the enzyme no longer works properly.

Like all catalysts, enzymes take part in the reaction - that is how they provide an alternative reaction pathway. But they do not undergo permanent changes and so remain unchanged at the end of the reaction. They can only alter the rate of reaction, not the position of the equilibrium

DNA Helicase

Explanation:

The process of DNA replication is very complex and requires a variety of proteins in the form of Enzymes.

The DNA replication starts at the site which is about 245 base pairs long and is rich in AT sequences called Origin of replication. The origin of replication recognised by an enzyme called DNA helicase which breaks the hydrogen bonds present between the bases and unwinds the DNA. The RNA primase enzymes then synthesizes an RNA primer which gets attached and to which DNA polymerase binds and add nucleotides.

Thus, the first enzyme that binds to the DNA is DNA helicase.