Tyrosine Kinase/Adaptors


Protein Tyrosine Kinase




The protein tyrosine kinases (PTKs) are a large and diverse multigene family found only in Metazoans and they are a large family of enzymes that catalyze the phosphorylation of protein molecules. Their principal functions involve the regulation of multicellular aspects of the organism. Cell-to-cell signals concerning growth, differentiation, adhesion, motility, and death, are frequently transmitted through tyrosine kinases.

The human protein kinase gene family, which consists of 518 members, along with 106 pseudogenes, is the second-largest enzyme family and the fifth-largest gene family in humans. Chromosomal mapping has provided evidence indicating that, out of the 518 protein kinase genes, 244 maps to either disease loci or cancer amplicons, further highlighting the therapeutic potential of protein kinase inhibitors and their targets[1].



Fig.1 Protein kinases contributing to leukaemia (highlight in blue)[2]


Classification of PTKs


Protein kinases are classified into two main families based on the ability to phosphorylate either tyrosine or serine and threonine residues. The human genome contains 90 unique TK genes, out of which, 58 are receptor types, distributed into 20 subfamilies, and 32 are non-receptor types grouped into 10 subfamilies. PTK can be divided into non-receptor type and receptor type according to whether it is present in the membrane receptor. The receptor type is total of 18 kinds, including ALK receptor family, FGFR family, PDGFR family and other families. The non-receptor type is total of 10 kinds, such as ABL1 and BCR-ABL family, ACK, FAK family and others. They can catalyze the phosphorylation of tyrosine residues of various substrate proteins, which plays an important role in cell growth, proliferation and differentiation.





[1] Manning G., Whyte D.B., Martinez R., et al. The protein kinase complement of the human genome. Science. 2002, 298: 1912-1934.

[2] Kalpana K. Bhanumathy, Amrutha Balagopal, Frederick S. Vizeacoumar, et al. Protein Tyrosine Kinases: Their Roles and Their Targeting in Leukemia. Cancer. 2021, 13(2): 184.

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