Tyrosine’s hydroxyl lone pair is a key structural and functional feature of this essential amino acid. Its lone-pair electrons participate in hydrogen bonding, influencing protein folding, stability, and interactions. This lone pair also contributes to tyrosine’s reactivity in enzymatic reactions, such as phosphorylation by tyrosine kinases, a crucial step in signal transduction pathways. The lone pair’s accessibility and polarity make it a versatile target for chemical modifications, including nitration and sulfation, which further diversify tyrosine’s biological roles.
