Definition: A conversion in which a pool of macromolecules are degraded into their elementary units. Usage: This conversion always has a direction of left-to-right and is irreversible. Degraded molecules are always represented on the left, degradation products on the right. Comments: Degradation is a complex abstraction over multiple reactions. Although it obeys law of mass conservation and stoichiometric, the products are rarely specified since they are ubiquitous. Example: Degradation of a protein to amino acids.
Source:http://www.biopax.org/release/biopax-level3.owl#Degradation