Prolyl and lysyl hydroxylases in collagen synthesis.

Collagens are the most abundant proteins in the extracellular matrix. They provide a framework to build organs and tissues and give structural support to make them resistant to mechanical load and forces. Several intra- and extracellular modifications are needed to make functional collagen molecules, intracellular post-translational modifications of proline and lysine residues having key roles in this. In this article we provide a review on the enzymes responsible for the proline and lysine modifications, i.e. collagen prolyl 4-hydroxylases, 3-hydroxylases and lysyl hydroxylases, and discuss their biological functions and involvement in diseases.