Tyrosine phosphorylation

Tyrosine phosphorylation is the addition of a phosphate (PO₄) group to the amino acid tyrosine on the protein. This transfer of phosphate group from ATP to the amino acid tyrosine on the protein is made possible through enzymes called tyrosine kinases. Tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity.