Biodegradable polymers are polymers degraded by the avtion of microorganism. These microrganisms can be bacteria, fungi, algae and others. These microorganisms produce enzymes that can catalyze biochemical reactions that will degrade the polymer. The enzymes don't necessarily have to directly catalyze the reactions which degrade the polymers, the enzymes can just catalyze reactions that produce reactive molecules, these molecules then can react with the polymer chain and degrade it. Directly or indirectly, if enzymes are required to degrade a polymers than that polymer is biodegradable.

Enzymes are structurally very complex and specialized proteins produced by cells to catalyze reactions o biological importance.