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 Flavor Ingredients has been incorporated into food products currently being marketed by Nestlé in the Pacific Rim and Latin America.
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. S2383 has received U.S. FEMA GRAS (Generally Recognized As Safe) status, which allows it to be incorporated into products in the U.S. as well as additional countries. Firmenich, SA has an exclusive license from Senomyx for worldwide commercialization of the S2383 Sucralose Enhancer. Use of Senomyx’s patented sweet receptor methodology also resulted in our discovery of S6973, a highly effective enhancer of the natural sweetener sucrose (table sugar) and additional sucrose enhancers. S6973 received a FEMA GRAS determination in October 2009.
Bitter Receptors. The response to bitter substances is mediated by a novel family of GPCRs termed T2Rs. The hT2R family is composed of about 25 receptors, each of which recognizes a different class of bitter substances. Senomyx’s analyses predict that 22 of these receptors are the primary means by which individuals sense bitter tastants. Using our receptor-based assays and optimization processes, we have identified blockers for 18 different bitter receptors, and screening is ongoing to find blockers for the remaining receptors. In February 2009, Senomyx announced that S0812 and additional Bitter Blockers met the criteria established by one of our collaborators for reducing the bitterness of their products. In conjunction with that collaborator, Senomyx has initiated development activities intended to support regulatory filings for these promising Bitter Blockers.
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 present on the surface of taste bud cells. During 2008, Senomyx reported a major scientific finding with the discovery of SNMX-29, the protein the Company believes is the primary receptor responsible for human salt taste. Using new proprietary screening assays based on SNMX-29, we have identified more than 250 enhancers of both sodium chloride (which is table salt) and potassium chloride that are active in the assays.
