Insulin. Is it a hormone or an enzyme, and why does it matter? Given that insulin is a chemical that activates a biological function, it is natural to wonder whether it is an enzyme or a hormone. Whereas both enzymes and hormones are chemicals and both are needed to activate biological functions, there is a critical difference between the two. Enzymes are basically catalysts, while h... https://www.freedomfromdiabetes.org/blog/post/diabetic-insulin-and-its-importance/2834