Glutamate

Direct Blue 1 (Pontamine sky blue), a counterstain for background autofluorescence in immunofluorescence histochemistry, structurally resembles glutamate and operates as a potent, competitive VGLUT inhibitor, not impacting plasma membrane transporters. This compound stands out as the inaugural small molecule PrP ligand to inhibit Aβ binding.

Evans blue (C.I. 23860) is an effective inhibitor of glutamate uptake by synaptic vesicles and also acts as an antagonist of AMPA/kainate receptors. Evans blue is a water-soluble azo fluorescent dye that binds to serum albumin and is used to detect vascular permeability, blood-brain barrier integrity, and permeability.

8-Azidoadenosine-5'-O-diphosphate (8-azido-ADP), a clickable variant of the ATP precursor and purinergic receptor ligand ADP, serves as a photoaffinity label for proteins including glutamate dehydrogenase (GDH) isoproteins from bovine brains, as well as eukaryotic translation initiation factor 2 (eIF2) and guanine nucleotide exchange factor (GEF) from rabbit reticulocytes. Radiolabeled versions of this compound facilitate the identification of these protein interactions.

TNP-GTP, a fluorescent derivative of guanosine 5'-triphosphate (GTP), essential for protein synthesis and gluconeogenesis, exhibits an emission peak at 552 nm when excited at 410 nm in water. Its fluorescence intensity increases and emission peaks shift to 544 nm and 532 nm in 40% and 80% N,N-dimethylformamide, respectively, due to the solvent's lower polarity compared to water. As a potent inhibitor of glutamate dehydrogenase (Ki = 2.7 μM), TNP-GTP enhances fluorescence and shifts its emission to 545 nm upon binding to this enzyme, a process reversible by GTP addition. Additionally, it serves as an antagonist to purinergic P2X2 and P2X2/3 receptors (IC50s = 0.4 and 1.2 nM, respectively) and selectively inhibits rat soluble guanylyl cyclase (sGC; Ki = 11 nM) over bovine liver glutamate dehydrogenase (GDH; Ki = 2.7 µM) and the calmodulin-dependent B. pertussis adenylyl cyclase (AC) toxin, with inhibition constants of 20 µM and 320 µM in the presence of manganese and magnesium, respectively.