bout : Enzymes are complex proteins that your body needs in order to work properly. An enzyme called creatine phosphokinase (CPK) is important for muscle function. The CPK isoenzymes test is a way to measure the levels of this enzyme in your bloodstream. This enzyme can be broken into three parts:- 1. CPK 1 : mainly found in our brain and lungs. 2. CPK 2: mostly found in our heart. 3. CPK 3: found in our skeletal muscle. The CPK isoenzymes test checks the levels of these enzymes in your blood. This can help your doctor identify the areas of your body that have been damaged.