Insulin is not a digestive enzyme. Digestive enzymes play a crucial role in breaking down food into smaller molecules that can be absorbed by the body. Pepsin is a digestive enzyme produced in the stomach that helps break down proteins. Renin is an enzyme produced in the stomach that aids in the digestion of milk proteins. Amylopsin is an enzyme that assists in the digestion of starch and is produced by the pancreas. However, insulin is a hormone produced by the pancreas and is responsible for regulating blood sugar levels, not for the digestion of food. Insulin helps facilitate the uptake of glucose by cells for energy production and storage. Therefore, option 3, Insulin, is not a digestive enzyme.