Enzymes are a catalyst that speed up chemical reactions in your body. Enzymes are made up of proteins. Different protein structures make up different enzymes. Enzymes are very specific to the substrate they work on so only certain enzymes can participate in certain reactions. The active site on the enzyme is the space where the substrate attaches. Each type of enzyme will have a differently shaped active site that will only fit a specific substrate. The substrate will attach to the enzyme on the active site and the enzyme will help break the substrate down into products. Your body naturally makes many enzymes but enzymes can also be made synthetically in labs. The example below shows how an enzyme will break a substrate down into products.