The Ancient Immunoglobulin Domains of Peroxidasin Are Required to Form Sulfilimine Cross-links in Collagen IV.

The collagen IV sulfilimine cross-link and its catalyzing enzyme, peroxidasin, represent a dyad critical for tissue development, which is conserved throughout the animal kingdom. Peroxidasin forms novel sulfilimine bonds between opposing methionine and hydroxylysine residues to structurally reinforce the collagen IV scaffold, a function critical for basement membrane and tissue integrity. However, the molecular mechanism underlying cross-link formation remains unclear. In this work, we demonstrate that the catalytic domain of peroxidasin and its immunoglobulin (Ig) domains are required for efficient sulfilimine bond formation. Thus, these molecular features underlie the evolutionarily conserved function of peroxidasin in tissue development and integrity and distinguish peroxidasin from other peroxidases, such as myeloperoxidase (MPO) and eosinophil peroxidase (EPO).