Adenylylation is a posttranslational modification that can occur to molecules such as tyrosine residues. Adenylylation involves a phosphodiester bond between a hydroxyl group of the molecule undergoing adenylylation and the phosphate group of the adenosine monophosphate nucleotide (i.e. adenylic acid).
The degree of adenylylation depends on the ratio of glutamine to α-ketoglutarate: The higher this ratio the more monomers are adenylylated, thereby producing lower activity of glutamine synthetase; the lower the ratio the less monomers are adenylated and the higher activity of glutamine synthetase. A high ratio is a sign of cellular nitrogen sufficiency, whereas a low ratio is evidence of a limited nitrogen and the need for ammonia fixation by glutamine synthetase.
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- ^ Garrett, R.H., and C.M. Grisham. Biochemistry. 3rd ed. Belmont, CA: Thomas, 2007. 815-20