A question about enzymes digesting substrates.....?

So I read somewhere that the enzyme "polyphenol oxidase" is released when an apple is cut, causing the colorless phenol to be converted into brown melanin, which is the cause of apples browning when left in the air. And I know that one of the ways to prevent apple browning (other than putting citric acids) is to add in protease. The reason behind this method, i ume, is that protease breaks down the polyphenol oxidase( which is the protein). So I was wondering, enzymes can digest enzymes? I mean protease is the enzyme here, and it is breaking down the substrate polyphenol oxidase, which is also an enzyme????