The formation of a protein active site cross-link from the alpha-carboxyl carbon of residue n, an alanine, serine or cysteine, to the alpha-amino nitrogen of residue n+2, a glycine, and a dehydration to form a double bond to the alpha-amino nitrogen of residue n+1. This cross-linking is coupled with an oxidation of residue n+1 to form an active aldehyde.