Receptor Discovery
There are currently five recognized primary senses of taste: umami, which is the savory taste of glutamate, sweet, salt, bitter and sour. Scientists generally believe that each taste sensation is recognized by a distinct taste receptor or family of taste receptors on the surface of taste bud cells in the mouth or on the tongue. A taste receptor functions either by physically binding to a flavor ingredient in a process analogous to the way a key fits into a lock or by acting as a channel to allow ions to flow directly into a taste cell. The brain recognizes tastes by determining which of the numerous receptors in the mouth have been contacted by a given flavor ingredient. Savory, sweet and bitter ingredients bind to taste receptors called G protein-coupled receptors (GPCRs) that are specific to each taste. In contrast, the taste of salt and the sour taste are thought to be recognized by a different type of receptor.
Senomyx has been granted numerous patents in the U.S. and elsewhere regarding the human savory (umami), sweet, and bitter taste receptors. These patents cover the use of many receptor subunits and variants, as well as related taste receptor screening assays, for identifying new savory, sweet, and bitter blocking flavor ingredients. We also have patents pending related to the protein that we believe is the primary receptor responsible for salty taste.
The following summarizes the proteins involved in the perception of savory, sweet, bitter, and salty tastes and Senomyx’s related technologies.
Savory (Umami) Receptor. Glutamate is a natural component of foods including tomatoes, mushrooms, parmesan cheese, and meats. It is often added to foods in the form of MSG (monosodium glutamate) to provide a savory flavor. The human savory receptor is composed of two proteins called hT1R1 and hT1R3. The T1R proteins are members of the GPCR family and are expressed on the surface of certain taste bud cells. Senomyx used our patented umami receptor assay to identify new savory ingredients that can be added to foods or beverages to reduce or replace MSG, and to create new savory flavors. One of our Savory Flavors has been incorporated into food products currently being marketed by Nestlé in the Pacific Rim, Latin America, Africa, and the Middle East.
Sweet Receptor. The human sweet receptor is composed of two proteins called hT1R2 and hT1R3. The hT1R3 protein is shared in common with the savory receptor. Like the savory receptor, the sweet receptor is also a member of the GPCR family and is expressed on the surface of certain taste bud cells. Senomyx’s proprietary sweet receptor screening assay was used to discover S2383, a potent enhancer of the artificial sweetener sucralose. Use of Senomyx’s this methodology also resulted in our discovery of S6973, a highly effective enhancer of the natural sweetener sucrose (table sugar). Both S2383 and S6973 are currently being marketed by Firmenich SA. Most recently, Senomyx discovered S9632, a new sucrose enhancer with alternative desirable properties. We have initiated development activities in preparation for regulatory filings of S9632.
Bitter Receptors. The taste response to bitter substances is mediated by a novel family of GPCRs termed T2Rs. The hT2R family is composed of about 25 receptors that recognize different classes of bitter substances. Using our receptor-based assays and optimization processes, we have identified blockers for 22 different human bitter receptors. These blockers fall into two types, those that are specific to a single bitter receptor and those that block multiple bitter receptors. Two of our bitter blockers that can block the bitterness of a variety of bitter foods and beverages, S6821 and S7958, received FEMA GRAS (Generally Recognized As Safe) regulatory status in November, 2010.
Salt Receptor. In contrast to the GPCRs that mediate savory, sweet, and bitter tastes, sodium ions (and to a lesser extent, potassium ions) are thought to produce a salt taste via a different type of receptor or protein present on the surface of taste bud cells. Senomyx is exploring the role of various proteins that may be integral to the sensation of salty taste. This high-priority effort involves chemistry and biology approaches, including assessing components of Senomyx’s proprietary database of proteins found in taste buds. Senomyx believes that discovery of the protein or proteins that function as the salt taste receptor could lead to identifying a salt taste enhancer.
