Umami - The Fifth Taste

We all have learned from our childhood 4 tastes like - sweet, salty, sour and bitter BUT there is another basic taste called Umami ( Japanese meaning "flavor" or "taste" ). Umami as a separate taste was first identified in 1908 by Kikunae Ikeda @ Tokyo university.

• The umami taste is due to the detection of the carboxylate anion of glutamic acid, a naturally occurring amino acid common in meat, cheese, broth, stock, and other protein-heavy foods.
  

• Salts of glutamic acid, known as glutamates, easily ionize to give the same carboxylate form and therefore, Umami taste.

While the umami taste is due to glutamates, 5'-ribonucleotides such as guanosine monophosphate (GMP) and inosine monophosphate (IMP) greatly enhance its perceived intensity.

Actual taste receptor responsible for the sense of umami, a modified form of mGluR4 named "taste-mGluR4." Umami tastes are initiated by these specialized receptors, with subsequent steps involving secretion of neurotransmitters, including adenosine triphosphate (ATP) and serotonin.

clinical implications :-  

Protein-energy malnutrition is one of the leading causes of death in children worldwide. Increased understanding of amino acid taste receptors may help nutritionists target the appetites of protein-malnourished children to provide good-tasting dietary supplements that kids will readily accept.

UMAMI taste is common to savory products such as meat, cheese, and mushrooms.

: Science of Food goes like this :

Nobel Prize 2008 Chemistry

American scientists Martin Chalfie and Roger Y. Tsien and Osamu Shimomura of Japan won the 2008 Nobel Prize in chemistry
"for the discovery and development of the green fluorescent protein, GFP".

Glowing proteins – a guiding star for biochemistry


The green fluorescent protein GFP consists of 238 amino acids, linked together in a long chain. This chain folds up into the shape of a beer can. Inside the beer can structure the amino acids 65, 66 and 67 form the chemical group that absorbs UV and blue light, and fluoresces green.

The remarkable brightly glowing green fluorescent protein, GFP, was first observed in the beautiful jellyfish, Aequorea victoria in 1962. Since then, this protein has become one of the most important tools used in contemporary bioscience. With the aid of GFP, researchers have developed ways to watch processes that were previously invisible, such as the development of nerve cells in the brain or how cancer cells spread.
The story behind the discovery of GFP is one with the three Nobel Prize Laureates in the leading roles:

Osamu Shimomura first isolated GFP from the jellyfish Aequorea victoria, which drifts with the currents off the west coast of North America. He discovered that this protein glowed bright green under ultraviolet light.

Martin Chalfie demonstrated the value of GFP as a luminous genetic tag for various biological phenomena. In one of his first experiments, he coloured six individual cells in the transparent roundworm Caenorhabditis elegans with the aid of GFP.

Roger Y. Tsien contributed to our general understanding of how GFP fluoresces. He also extended the colour palette beyond green allowing researchers to give various proteins and cells different colours. This enables scientists to follow several different biological processes at the same time.

2008 Nobel Prize In Physiology Or Medicine

The Nobel Assembly at Karolinska Institutet has today decided to award The Nobel Prize in Physiology or Medicine for 2008 with one half to: Harald zur Hausen for his discovery of "human papilloma viruses causing cervical cancer" and the other half jointly to Françoise Barré-Sinoussi and Luc Montagnier for their discovery of "human immunodeficiency virus."




The award for HIV discovery is controversial because for many years, Montagnier and his colleagues at the Pasteur Institute in Paris were locked in a wrangle with Robert Gallo of the US National Institutes of Health over who actually discovered the virus.The Nobel citation mentions Gallo's contributions, but settles the dispute once and for all by declaring the French duo to be the true discoverers of the virus, just two years after the first cases of AIDS were reported in 1981.
Their discovery rapidly paved the way for tests to diagnose the disease in patients and screen blood donations for viral contamination.And by establishing at a molecular level how the virus wrecks the immune system by infecting CD4 cells, the duo enabled rapid development of today's antiretroviral drugs that combat the virus and stop infected people dying of the disease.

"Never before has science and medicine been so quick to discover, identify the origin and provide treatment for a new disease entity," says the Nobel prize citation.

Drug breakthrough

Montagnier and Barré-Sinoussi traced the virus after studying samples of white blood cells that clumped together in the swollen lymph nodes of patients. Lurking in these CD4 T helper lymphocytes, they detected activity of reverse transcriptase, the enzyme which enables the virus to multiply itself.
And through their microscopes, the duo observed viral particles budding out from the surface of infected cells.
Although it resembled a virus isolated by Gallo called HTLV-1, the French virus initially called lymphadenopathy associated virus turned out to be HIV-1.
In 1985, an international virus taxonomy consortium chose to name the virus Human Immunodeficiency Virus-1, or HIV-1.
Once it had been discovered, several groups proved that the virus causes AIDS. The first drugs arrived in 1987, and the race is now on to get the current antiretroviral drugs to all patients who need them, especially in poorer countries in Africa.
None of this would have been possible had it not been for the discovery of the virus itself by Montagnier, now at the World Foundation for AIDS Research and Prevention in Paris, and Barré-Sinoussi, still at the Pasteur Institute.

Persistent search

Harald zur Hausen of the German Cancer Research Center, Heidelberg, is credited with establishing the link between infection with the human papilloma virus (HPV), which causes genital warts, and cervical cancer.
His discoveries have led to development of two commercial vaccines to prevent cervical cancer: Gardasil and Cervarix.
Zur Hausen began his quest to prove that viruses caused cervical cancer in the 1970s, despite the scepticism of his peers.
After combing through the DNA of cervical cancer cells from biopsies for 10 years, he eventually found traces of HPV genetic material. In 1983, he established that a strain called HPV-16 had infected the cells.
A year later, he cloned HPV-16 and HPV-18 from patients with cervical cancer. Subsequently, the viruses have been found in 70% of cervical cancer biopsies throughout the world.

First cancer vaccine

More than 5% of all cancers are caused by these viruses, and HPV is the most commonly sexually-transmitted agent, afflicting 50 to 80% of the world population.
Subsequently, zur Hausen unravelled the complex molecular route by which HPV causes cancer, enabling development of the vaccines that provide 95% protection from the high-risk HPV-16 and HPV-18.
"He was very much against the prevailing thought at the time, but doggedly pursued his theory that a virus was responsible," says Nicholas Kitchin, medical director at Sanofi.
"Eventually, he proved it, not just identifying that HPV was the cause, but allowing others to take that forward to development of the world's first true cancer vaccine," he says.
So far, says Kitchin, Gardasil has been licensed in 105 countries and 30 million women have received it

The 1000 Genomes Project

The 1000 Genomes Project, launched in January 2008, is an international research effort to establish by far the most detailed catalogue of human genetic variation. Scientists plan to sequence the genomes of at least one thousand anonymous participants from a number of different ethnic groups within the next three years, using newly developed faster and less expensive sequencing technologies.
"The 1000 Genomes Project will examine the human genome at a level of detail that no one has done before," said Richard Durbin, Ph.D., of the Wellcome Trust Sanger Institute, who is co-chair of the consortium. "Such a project would have been unthinkable only two years ago. Today, thanks to amazing strides in sequencing technology, bioinformatics and population genomics, it is now within our grasp. So we are moving forward to build a tool that will greatly expand and further accelerate efforts to find more of the genetic factors involved in human health and disease."
"This new project will increase the sensitivity of disease discovery efforts across the genome five-fold and within gene regions at least 10-fold," said NHGRI Director Francis S. Collins, M.D., Ph.D.
The 1000 Genomes Project will map not only the single-letter differences in people's DNA, called single nucleotide polymorphisms (SNPs), but also will produce a high-resolution map of larger differences in genome structure called structural variants. Structural variants are rearrangements, deletions or duplications of segments of the human genome. The importance of these variants has become increasingly clear with surveys completed in the past 18 months that show these differences in genome structure may play a role in susceptibility to certain conditions, such as mental retardation and autism.
"This project will examine the human genome in a detail that has never been attempted -- the scale is immense. At 6 trillion DNA bases, the 1000 Genomes Project will generate 60-fold more sequence data over its three-year course than have been deposited into public DNA databases over the past 25 years," said Gil McVean, Ph.D., of the University of Oxford in England, one of the co-chairs of the consortium's analysis group. "In fact, when up and running at full speed, this project will generate more sequence in two days than was added to public databases for all of the past year."

When is genome project finished ?

When sequencing a genome, there are usually regions that are difficult to sequence (often regions with highly repetitive DNA). Thus, 'completed' genome sequences are rarely ever complete, and terms such as 'working draft' or 'essentially complete' have been used to more accurately describe the status of such genome projects. Even when every base pair of a genome sequence has been determined, there are still likely to be errors present because DNA sequencing is not a completely accurate process. It could also be argued that a complete genome project should include the sequences of mitochondria and (for plants) chloroplasts as these organelles have their own genomes.

It is often reported that the goal of sequencing a genome is to obtain information about the complete set of genes in that particular genome sequence. The proportion of a genome that encodes for genes may be very small (particularly in eukaryotes such as humans, where coding DNA may only account for a few percent of the entire sequence). However, it is not always possible (or desirable) to only sequence the coding regions separately. Also, as scientists understand more about the role of this noncoding DNA (often referred to as junk DNA)
(http://genomevolution.blogspot.com), it will become more important to have a complete genome sequence as a background to understanding the genetics and biology of any given organism.

In many ways genome projects do not confine themselves to only determining a DNA sequence of an organism. Such projects may also include gene prediction to find out where the genes are in a genome, and what those genes do. There may also be related projects to sequence ESTs or mRNAs to help find out where the genes actually are.