Common methods available to detect kinase activities include:
A traditional technique for detecting kinase activity, radiometric protocols involve the use of a 32P-labeled ATP. The steps can be adapted for use with immunoprecipitated cultured cells or with recombinant affinity-tagged purification over different reaction conditions.
To assess kinase activity, a buffer made using ATP, a protein inhibitor, and reducing agent, is combined with the kinase sample and incubated. A stop solution is added and SDS-PAGE is then performed. Upon analysis, kinase activity is calculated in units of nanomole phosphate transferred per min per mg kinase.
A highly sensitive and versatile technique, Qualitative polymerase chain reaction (qPCR) is capable of quantitating multiple kinases simultaneously on a single panel with high throughput capabilities. This allows researchers to detect the associated DNA label and compare it to known controls to determine the amount of kinase captured in test samples. qPCR can also be used to determine dissociation constants for kinase interactions and to detect type I, type II, and allosteric kinase inhibitors.
A significant advantage of using qPCR to detect kinase activities is that it does not require ATP, which allows researchers to measure only true thermodynamic interaction affinities rather than relying on IC50 values like most other techniques.
There are multiple fluorescent methods that can be used to detect kinase activity without the use of radioactivity.
Liquid Chromatography-Mass Spectrometryare phosphoproteomic techniques that enable the unbiased identification of phosphorylation by highly selective enrichment of phosphopeptides. The amount of phosphorylated proteins and phosphosites in a sample determines the observability of kinase activity. LC-MS/MS enables large-scale identification of phosphorylated peptides and phosphosite localization, providing crucial information on the relationship between kinase activity and physiology.
Sandwich ELISA is a rapid, sensitive, and cost-effective method that uses purified enzyme preparations, adherent, or suspension cell culture extracts for monitoring and assessing kinase activity. It also enables detection of substrate specificity in samples.