Enzymes are made up of proteins known as amino acids. The complex protein structure of enzymes allow them to attach to substrate molecules and speed up chemical reactions. Enzymes are produced by the human body but can also be synthetically produced in a lab environment.
Lactase is an enzyme used to break down milk products. If a person's body is unable to produce lactase, it can be taken as a pill. Lactase made in a lab and packaged in a pill form has the same structure as lactase produced by the body and will allow an individual to digest milk products.