Autophosphorylation is a biochemical process in which a phosphate is added to a protein kinase by itself. In eukaryotes, autophosphorylation takes place by the addition of a phosphate group to serine, threonine, or tyrosine residues in protein kinases.1, 2 Most of the phosphate groups added are from nucleoside triphosphates such as ATP.1 The name is due to the phosphorylation reaction that takes place through its own enzymatic activity. This process is essential in cell signaling. It causes a conformational change to expose or hide catalytic or allosteric sites, thereby regulating kinase activity (e.g. substrate binding or molecular recognition).1 Apart from this, autophosphorylation is also reported to be involved in enabling cells for endocytosis and proteolysis.3
1Petsko, GA and Ringe, D 2009, 'Protein Structure and Function’, Oxford University Press Inc., New York, U.S.A
2 Summers, K. C.; Shen, F.; Sierra Potchanant, E. A.; Phipps, E. A.; Hickey, R. J.; Malkas, L. H. (2011). "Phosphorylation: The Molecular Switch of Double-Strand Break Repair". International Journal of Proteomics 2011: 1.
3 Smith, J. A.; Francis, S. H.; Corbin, J. D. (1993). "Autophosphorylation: A salient feature of protein kinases". Molecular and cellular biochemistry. 127-128: 51–70.