Tyrosine modifications.A, tyrosine modifications targeting the hydroxyl group of the phenolic ring are sulfation, phosphorylation, and AMPylation (referred to as adenylation). Tyrosine nitration and halogenation (addition of chloride/bromide onto the ortho carbon) are the newest entries in the biological repertoire of tyrosine PTMs. B, biological pathways and chemistry that contributes to tyrosine nitration. PTMs, posttranslational modifications.