Could targeting Adenosine Kinase help lead to treatments for neurological disorders and chronic pain? Adenosine, one of four nucleoside building blocks to DNA and RNA, has a shielding effect on a wide range of conditions, including inflammation, various forms of neuronal hyperexcitability, and/or toxicity, including hypoxia, seizures, and chronic pain. This cellular activity modulator brings balance to cells exposed to trauma and stress.3 As necessary in the homeostasis of imperative cellular activities are the molecules that regulate adenosine itself, such as adenosine kinase (ADK), which mediates the phosphorylation of adenosine resulting in adenosine monophosphate (AMP). The phosphorylation/dephosphorylation feedback loop from adenosine to AMP is known as the adenosine futile cycle.1
Furthermore, Cluster of Differentiation 39 (CD39) is an ectonucleotidase (an enzyme that catalyzes the formation of nucleosides) that regulates adenosine via dephosphorylation of adenosine triphosphate (ATP). It turns out, regulating adenosine is an extremely significant responsibility as it is not only an abundant molecule inside the body and a building block for DNA but is also used in treating a range of ailments.
While adenosine has protective qualities and is a component of many enzyme cofactors, such as FADH, NAD(P)H, and coenzyme A, low levels are damaging to mitochondrial function as well as cellular metabolism.1
The role of ADK in regulating adenosine, therefore, many cellular functions, makes it a model candidate for potential therapeutics. To that point, researchers have found that ADK inhibitors can enhance endogenous adenosine levels at specific sites that could ultimately lead to drug therapies in areas where adenosine has a protective effect, such as inflammation or chronic pain.3 This is thought to be due to the intracellular blocking of ADK that increases extracellular concentrations of adenosine.
Moreover, deficiencies in ADK itself have been linked to liver disease, hypermethioninemia, and encephalopathy.1 Disruption in the adenosine futile cycle has a multitude of consequences. As an essential amino acid, methionine plays a critical role in metabolism as well as acting as a substrate for other amino acids. A proper balance is necessary in order to carry out these vital functions.
Adenosine Kinase Activity Assay
Motives for targeting ADK in pharmaceutical treatments are obviously plentiful. Whether studying the effects of an ADK inhibitor on the concentration of adenosine or specifically interested in ADK or adenosine individually, there’s an assortment of Transcreener® Assay Kits suitable for the research. Each assay directly detects the common product of an enzymatic reaction and can be used to target an entire target family. To measure ADP produced by ADK it is suggested to use the Transcreener ADP² Adenosine Kinase Assay.
Ways to utilize Transcreener Assay Kits in adenosine research:
- Screen for small molecule inhibitors
- Determine enzymatic activity
- Profile inhibitor potency / determine IC50 values
- Measure residence time / off-rate / dissociation of lead molecules with target
- Inhibitor selectivity profiling
- Mechanism of action studies
The easy-to-use universal assay limits the need for specific reagents. There are different formats (fluorescence polarization (FP), time-resolved FRET (TR-FRET), and fluorescence intensity (FI)) depending on the intended research.
- Bjursell, M. K., Blom, H. J., Cayuela, J. A., Engvall, M. L., Lesko, N., Balasubramaniam, S., … Wedell, A. (2011). Adenosine kinase deficiency disrupts the methionine cycle and causes hypermethioninemia, encephalopathy, and abnormal liver function. American Journal of Human Genetics, 89(4), 507–515. https://doi.org/10.1016/j.ajhg.2011.09.004
- Borea, P. A., Gessi, S., Merighi, S., Vincenzi, F., & Varani, K. (2017). Pathological overproduction: the bad side of adenosine. British Journal of Pharmacology, 174(13), 1945–1960. https://doi.org/10.1111/bph.13763
- Jarvis, M. F. (2019). Therapeutic potential of adenosine kinase inhibition—Revisited. Pharmacology Research and Perspectives, 7(4), 1–7. https://doi.org/10.1002/prp2.506