The enzyme that destroys the ability of the transforming principle to function is DNase, or deoxyribonuclease.

Here's why:

* The Transforming Principle: In the classic experiment by Avery, MacLeod, and McCarty, they discovered that the transforming principle, the substance responsible for transferring genetic information, was DNA.

* DNase's Role: DNase is an enzyme specifically designed to break down DNA. When DNase was added to the mixture containing the transforming principle, it destroyed the DNA, preventing the transformation of bacteria.

* Other Enzymes: RNase (ribonuclease) and protease, enzymes that break down RNA and proteins respectively, did not inhibit the transforming principle. This confirmed that DNA was the key component responsible for the observed genetic transformation.

This experiment was crucial in establishing DNA as the carrier of genetic information.