Citrullinated Peptide Synthesis

The amino acid citrulline is not coded for by DNA directly, however, several proteins are known to contain citrulline as a result of a posttranslational modification. These citrulline residues are generated by a family of enzymes called peptidylarginine deiminases (PADs), which convert arginine into citrulline in a process known as citrullination or deimination. It has become clear in recent years that histones, fibronectin, myelin basic protein (MBP), as well as other cellular proteins, can be modified by post-translational changes during epigenetic regulation in the cell. These modifications include acetylation, methylation, phosphorylation, ubiquitination and citrullination, among others. Histone modifications induce changes to the structure of chromatin and thereby affect the accessibility of the DNA strand to transcriptional enzymes, resulting in activation or repression of genes associated with modified histones. So far, citrulline modifications have been connected with  autoimmune disorders such as multiple sclerosis and rheumatoid arthritis. Biosynthesis offers citrulline incorporation into any peptide sequence to help researchers study the effect of these modifications in vivo or in vitro.