A process for isolating an antagonist of the bitter taste receptor activity of the polypeptide encoded by a polynucleotide selected from the group consisting of: (a) polynucleotides encoding at least the mature form of the polypeptide having the deduced amino acid sequence as shown in SEQ ID NO: 37; (b) polynucleotides having the coding sequence, as shown in SEQ ID NO: 38 encoding at least the mature form of the polypeptide; (c) polynucleotides encoding a fragment or derivative of a polypeptide encoded by a polynucleotide of any one of (a) to (b), wherein in said derivative not more than 45 amino acid residues are conservatively substituted compared to said polypeptide, and said fragment or derivative has bitter taste receptor activity; (d) polynucleotides which are at least 85% identical to a polynucleotide as defined in any one of (a) to (c) and which code for a polypeptide having bitter taste receptor activity; and (e) polynucleotides the complementary strand of which hybridizes under stringent conditions to a polynucleotide as defined in any one of (a) to (d) and which code for a polypeptide having bitter taste receptor activity; comprising: contacting said polypeptide or a host cell genetically engineered with said polynucleotide or with a vector containing said polynucleotide with a potential antagonist; determining whether the potential antagonists antagonizes the bitter taste receptor activity of said polypeptide further comprising the contacting of the polypeptide or the host cell genetically engineered with said polynucleotide or with a vector containing said polynucleotide with an agonist selected from the group consisting of strychnine, brucine, denatonium benzoate, and absinthine and functional derivatives thereof, wherein a functional derivative elicits at least 20% of the bitter taste receptor activity when compared to unmodified strychnine, brucine, denatonium benzoate or absinthine, respectively, wherein the bitter taste receptor activity is a change of an intracellular messenger selected from the group consisting of Ca2 +, IP 3 and cAMP. (a) polynucleotides encoding at least the mature form of the polypeptide having the deduced amino acid sequence as shown in SEQ ID NO: 37; (b) polynucleotides having the coding sequence, as shown in SEQ ID NO: 38 encoding at least the mature form of the polypeptide; (c) polynucleotides encoding a fragment or derivative of a polypeptide encoded by a polynucleotide of any one of (a) to (b), wherein in said derivative not more than 45 amino acid residues are conservatively substituted compared to said polypeptide, and said fragment or derivative has bitter taste receptor activity; (d) polynucleotides which are at least 85% identical to a polynucleotide as defined in any one of (a) to (c) and which code for a polypeptide having bitter taste receptor activity; and (e) polynucleotides the complementary strand of which hybridizes under stringent conditions to a polynucleotide as defined in any one of (a) to (d) and which code for a polypeptide having bitter taste receptor activity; comprising: contacting said polypeptide or a host cell genetically engineered with said polynucleotide or with a vector containing said polynucleotide with a potential antagonist; determining whether the potential antagonists antagonizes the bitter taste receptor activity of said polypeptide further comprising the contacting of the polypeptide or the host cell genetically engineered with said polynucleotide or with a vector containing said polynucleotide with an agonist selected from the group consisting of strychnine, brucine, denatonium benzoate, and absinthine and functional derivatives thereof, wherein a functional derivative elicits at least 20% of the bitter taste receptor activity when compared to unmodified strychnine, brucine, denatonium benzoate or absinthine, respectively, wherein the bitter taste receptor activity is a change of an intracellular messenger selected from the group consisting of Ca2 +, IP 3 and cAMP. contacting said polypeptide or a host cell genetically engineered with said polynucleotide or with a vector containing said polynucleotide with a potential antagonist; determining whether the potential antagonists antagonizes the bitter taste receptor activity of said polypeptide