Activity-based detection of enzymes

Activity-based protein profiling (ABPP) is a chemical proteomic strategy in which active-site-directed covalent probes are used to profile the functional states of enzymes in complex proteomes. Activity-based probes (ABPs) can distinguish active enzymes from their inactive zymogens or inhibitor-bound forms. They contain a reactive group intended to modify enzyme active sites covalently and a reporter group (typically rhodamine or biotin) that assists in detection and identification of protein targets. 

Gel-based ABPP enables visualization of labeling events using gel electrophoresis accompanied by in-gel fluorescence (rhodamine) or 

A competitive version of ABPP identifies the target(s) and assesses the selectivity of an enzyme inhibitor in biological systems by gauging how well the inhibitor slows the enzyme s reaction with an ABP. For example, fluorophosphonate ABP 3 was used to profile the selectivity of fatty acid amide hydrolase (FAAH) inhibitors within the serine hydrolase superfamily [27] (FAAH hydrolyzes endocannabinoids such as anandamide). Serine hydrolases that exhibited reduced labeling by the probe in the presence of inhibitor were scored as targets of the inhibitor. Urea FAAH inhibitors exemplified by PF-3845 (5) that covalently modify the active-site serine nucleophile of FAAH were found to be exquisitely selective for FAAH in brain and liver 

Another ABPP platform integrates click chemistry (CC), where an alkyne or azide group in the ABP acts as a latent attachment point for a reporter tag [34,35]. Replacing bulky reporter groups with an alkyne extends ABP design to include probes that function in live cells and 

Bogy o s group developed several ABPs for cysteine proteases with epoxide, vinyl sulfone, and acyloxymethyl ketone reactive groups [42,43]. Particularly noteworthy is DCG04 (4), a biotinylated papain-family protease inhibitor with an epoxide reactive group that targets 

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