Among our basics senses, taste and our gustatory system allow us to perceive and recognize essential chemical nutrients present in food. Human can detect and discriminate five basics taste (sweet, bitter, sour, salty and umami) and recent studies proposed a sixth taste for fat. The umami taste is described as a « savory » sensation elicited mainly by L-amino acids and is thought to serve as an indicator of protein rich foods and promote feeding. The umami taste receptor is a heterodimeric receptor composed of the T1R1 and T1R3 subunits. These subunits belong to the family class C G protein-coupled receptors (GPCRs) and are constituted by a large N-terminal domain (NTD) linked to the transmembrane domain by a cysteine-rich region. The human T1R1/T1R3 receptor responds specifically to L-Glutamate (L-Glu) and L-Aspartate (L-Asp) with a response potentiated by 5’ ribonucleotides (IMP, GMP), which also elicit umami taste by themselves. It has been shown that whereas L-Glu binds to the hinge region of the T1R1-NTD and induce its closure, 5’ ribonucleotides bind to an adjacent site close to the opening and stabilise the T1R1-NTD in closed conformation. In contrast the functional role of T1R3-NTD in the umami compound detection remains largely unknown. In the present study, we report the ligand binding properties of recombinantly expressed T1R1- and T1R3-NTDs. The proteins overexpressed in Escherichia coli as insoluble aggregated protein (inclusion bodies) were solubilised, in vitro refolded and purified by two-step chromatography procedure. Circular dichroism and SEC-MALS analyses demonstrated that purified proteins are correctly refolded as monomeric form. Fluorescence spectroscopy demonstrated that T1R1- and T1R3-NTDs are both able to bind L-Glu and IMP with micromolar affinity. In summary, our results demonstrate the contribution of each subunit to the heterodimeric receptor function for the detection of these umami compounds.