TYROSINE KINASE

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.

Contents

Groups

Receptor

Cytoplasmic/non-receptor

Clinical significance

External links

Groups

The tyrosine kinases are divided into two groups:

★ those that are cytoplasmic proteins.

★ the transmembrane receptor-linked kinases.

Receptor

:''See main article at receptor tyrosine kinase''
In humans, there are 58 receptor-linked protein-tyrosine kinases ().
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).

Cytoplasmic/non-receptor

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

Clinical significance

Tyrosine kinase is particularly important today because of its implications in the treatment of cancer.

External links

★