Regioisomeric family of novel fluorescent substrates for SHIP2

SHIP2 (SH2-domain containing inositol 5-phosphatase type 2) is a canonical 5-phosphatase which, through its catalytic action on PtdInsP3, regulates the PI3K/Akt pathway and metabolic action of insulin. It is a drug target but there is limited evidence of inhibition of SHIP2 by small molecules in the literature. With the goal to investigate inhibition, we report a homologous family of synthetic, chromophoric benzene phosphate substrates of SHIP2 that display the headgroup regiochemical hallmarks of the physiological inositide substrates that have proved difficult to crystallize with 5-phosphatases. Using time-dependent density functional theory (TD-DFT), we explore the intrinsic fluorescence of these novel substrates and show how fluorescence can be used to assay enzyme activity. The TD-DFT approach promises to inform rational design of enhanced active site probes for the broadest family of inositide-binding / metabolizing proteins, whilst maintaining the regiochemical properties of bona fide inositide substrates.