Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists discover protein receptor for carbonation taste

19.10.2009
In 1767, chemist Joseph Priestley stood in his laboratory one day with an idea to help English mariners stay healthy on long ocean voyages.

He infused water with carbon dioxide to create an effervescent liquid that mimicked the finest mineral waters consumed at European health spas. Priestley's man-made tonic, which he urged his benefactors to test aboard His Majesty's ships, never prevented a scurvy outbreak.

But, as the decades passed, his carbonated water became popular in cities and towns for its enjoyable taste and later as the main ingredient of sodas, sparkling wines, and all variety of carbonated drinks.

Missing from this nearly 250-year-old story is a scientific explanation of how people taste the carbonation bubbling in their glass. In this week's issue of the journal Science, researchers at the National Institute of Dental and Craniofacial Research (NIDCR), part of the National Institutes of Health, and their colleagues from the Howard Hughes Medical Institute at the University of California, San Diego (UCSD) report that they have discovered the answer in mice, whose sense of taste closely resembles that of humans.

They found that the taste of carbonation is initiated by an enzyme tethered like a small flag from the surface of sour-sensing cells in taste buds. The enzyme, called carbonic anhydrase 4, interacts with the carbon dioxide in the soda, activating the sour cells in the taste bud and prompting it to send a sensory message to the brain, where carbonation is perceived as a familiar sensation.

"Of course, this raises the question of why carbonation doesn't just taste sour," says Nicholas Ryba, Ph.D., a senior author of this study and an NIDCR scientist. "We know that carbon dioxide also stimulates the mouth's somatosensory system. Therefore, what we perceive as carbonation must reflect the combination of this somatosensory information with that from taste."

A somatosensory system transmits sensory information within the body from protein receptors to nerve fibers and onward to the brain, where a sensation is perceived. Common sensory information includes taste, touch, pain, and temperature.

Ryba added that the taste of carbonation is quite deceptive. "When people drink soft drinks, they think that they are detecting the bubbles bursting on their tongue," he said. "But if you drink a carbonated drink in a pressure chamber, which prevents the bubbles from bursting, it turns out the sensation is actually the same. What people taste when they detect the fizz and tingle on their tongue is a combination of the activation of the taste receptor and the somatosensory cells. That's what gives carbonation its characteristic sensation."

Although some chefs might disagree, food does not tickle the taste buds that line the upper surface of the tongue, roof of the mouth, and upper esophagus. Rather the salt in a pretzel or the sugars in a chocolate drop bind to matching taste receptor cells clustered in our taste buds.

Scientists believe that our sense of taste generates only a limited palate of distinct qualities: the familiar sweet, sour, salty, bitter and savory tastes. Much of the flavor of food (the "tickling of taste buds") comes from a combination of this taste information with input from other senses like touch and smell.

Over the past decade, there has been tremendous progress in identifying the basis for detection of the five major taste qualities. Indeed, the laboratories of Charles Zuker, Ph.D., a senior author of this study from UCSD, and Ryba have previously teamed up to identify the receptor proteins and cells responsible for sweet, bitter, and savory taste and the receptor cells for sour detection. But can our sense of taste detect other flavors?

Recent work from a number of groups has suggested taste buds might detect other qualities, such as fat and metallic tastes. It also indicated that the gas carbon dioxide induces strong responses in taste nerves. The body senses carbon dioxide on many levels – in the somatosensory system (including touch and pain), smell, and in the brain and blood to control respiration. But how it is detected in taste was quite unclear.

This prompted Jayaram Chandrashekar, Ph.D., lead author of the study and a scientist at UCSD, to explore the taste of carbonation. Together with David Yarmolinsky and Lars von Buchholtz, Ph.D., co-authors of the paper, he discovered that the enzyme called carbonic anhydrase 4 is selectively expressed on the surface of sour taste receptor cells.

Carbonic anhydrase 4, or CA-IV, is one of a family of enzymes that catalyzes the conversion carbon dioxide to carbonic acid, which rapidly ionizes to release a proton (acid ion) and a bicarbonate ion (weak base). By so doing, carbonic anhydrases help to provide cells and tissues with a buffer that helps prevent excessive changes in pH, a measure of acidity.

The scientists found that if they eliminated CA-IV from the sour-sensing cells or inhibited the enzyme's activity, they severely reduced a mouse's sense of taste for carbon dioxide. Thus CA-IV activity provides the primary signal detected by the taste system. As CA-IV is expressed on the surface of sour cells, Chandrashekar and co-workers concluded that the enzyme is ideally poised to generate an acid stimulus for detection by these cells when presented with carbon dioxide.

Why do mammals taste carbonation? The scientists are still not sure if carbon dioxide detection itself serves an important role or is just a consequence of the presence of CA-IV on the surface of the sour cells, where it may be located to help maintain the pH balance in taste buds. As Ryba says, "That question remains very much open and is a good one to pursue in the future."

The article is titled "The Taste of Carbonation." The authors are Jayaram Chandrashekar, David Yarmolinsky, Lars von Buchholtz, Martyn Goulding, William Sly, Nicholas J. P. Ryba, and Charles S. Zuker.

The National Institute of Dental and Craniofacial Research (NIDCR) is the Nation's leading funder of research on oral, dental, and craniofacial health.

The National Institutes of Health (NIH) — The Nation's Medical Research Agency — includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases.

Bob Kuska | EurekAlert!
Further information:
http://www.nih.gov

More articles from Life Sciences:

nachricht The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences

nachricht Transforming plant cells from generalists to specialists
07.12.2016 | Duke University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>