Now, the fourth type of mechanism of regulation is actually regulating the amount of the enzyme that is present in the cell. And usually, as we'll discuss eventually this type of regulation is monitored on the level of transcription. So if we control the amount of transcription that takes place on a particular gene of interest that codes for some type of enzyme, we can ultimately control how much of that enzyme is produced inside that cell and in turn control the activity and the functionality level of that particular enzyme. Now, the final regulation method is basically something called an isoenzyme or isozyme. So what exactly is an isoenzyme? Well, an isoenzyme or isoenzymes, to be more correct, are these enzymes that differ in their sequence of amino acids and so they differ in the structure.