tyrosylprotein

Tyrosylprotein is a descriptive, not formal, term used in biochemistry to refer to proteins that involve tyrosine residues in key ways. It can denote proteins that contain tyrosine residues as part of their sequence or, more commonly, proteins that undergo tyrosine-specific post-translational modifications. The term therefore spans several distinct processes that modify or utilize tyrosine in proteins.

The most studied tyrosine-based modification is phosphorylation. In this process, enzymes called protein tyrosine kinases add a phosphate group to the phenolic hydroxyl of tyrosine, and protein tyrosine phosphatases remove it. Tyrosine phosphorylation is a central mechanism in signaling pathways that control cell growth, differentiation, metabolism, and immune responses. Abnormal tyrosine phosphorylation is linked to various diseases, including cancer and autoimmune disorders.

Tyrosylprotein sulfation is another important modification. In the Golgi apparatus, tyrosylprotein sulfotransferases transfer sulfate groups to specific tyrosine residues on secreted and membrane proteins, influencing protein–protein interactions, receptor binding, and trafficking. This modification affects molecules such as selectins and chemokine receptors, contributing to immune cell trafficking and vascular biology.

Beyond phosphorylation and sulfation, tyrosine residues can undergo iodination in thyroid hormone synthesis or participate in oxidative cross-linking that forms dityrosine bonds in extracellular matrices. Detection methods for tyrosine modifications include mass spectrometry and antibodies specific for phosphotyrosine or sulfotyrosine.

Overall, tyrosylproteins encompass a range of proteins whose function is driven by tyrosine-related chemistry, most notably signaling phosphorylation and extracellular functions mediated by sulfation.