Tyrosine kinase

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Tyrosine

Phosphate

ATP

Tyrosine kinases are a subclass of protein kinase, see there for the principles of protein phosphorylation

A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to a tyrosine residue in a protein. Tyrosine kinases are a subgroup of the larger class of protein kinases. Phosphorylation of proteins by kinases is an important mechanism in signal transduction for regulation of enzyme activity.

There are over 100 3D structures of tyrosine kinases available at the Protein Data Bank. An example is PDB 1IRK, the crystal structure of the tyrosine kinase domain of the human insulin receptor.

Most tyrosine kinases have an associated protein tyrosine phosphatase.

1 Groups
- 1.1 Receptor
- 1.2 Cytoplasmic/non-receptor
2 Clinical significance
3 External links

[edit] Groups

The tyrosine kinases are divided into two groups:

those that are cytoplasmic proteins.
the transmembrane receptor-linked kinases.

[edit] Receptor

See main article at receptor tyrosine kinase

In humans, there are 58 receptor-linked protein-tyrosine kinases (EC 2.7.10.1).

The hormones and growth factors that act on cell surface tyrosine kinase-linked receptors are generally growth-promoting and function to stimulate cell division (e.g., insulin, insulin-like growth factor 1, epidermal growth factor).

[edit] Cytoplasmic/non-receptor

In humans, there are 32 cytoplasmic protein tyrosine kinases (EC 2.7.10.2).

The first non-receptor tyrosine kinase identified was the v-src oncogenic protein. Most animal cells contain one or more members of the Src family of tyrosine kinases.

A chicken sarcoma virus was found to carry mutated version of the normal cellular Src gene.

The mutated v-src gene has lost the normal built-in inhibition of enzyme activity that is characteristic of cellular SRC (c-src) genes. SRC family members have been found to regulate many cellular processes.

For example, the T-cell antigen receptor leads to intracellular signalling by activation of Lck and Fyn, two proteins that are structurally similar to Src.