Figure 1: Schematic representation of Elastin fiber formation. Tropoelastin is expressed then secreted as a mature form of the protein into the extracellular matrix. This tropoelastin accumulates on the cell surface, first as small particles then as larger, approximately 1 micron spherules that are effectively massively associated coacervates of tropoelastin. At an undefined stage, the tropoelastin is subjected to oxidation by lysyl oxidase enzymes at a subset of lysines which subsequently participate in aldol condensation and Schiff base reactions to form cross-links. The forming elastin is introduced to microfibrils in the extracellular matrix by members of the fibulin protein family where the elastin fibers are assembled. The resulting elastin is a very stable and persistent structure that has an impressive ability to confer recoil to human tissues (Debelle and Alix, 1999;