Dr Hiroshi Ueno is leading a project entitled ‘Activation of GABA synthetic enzyme, glutamate decarboxylase, by spice and reduction of salt and elucidation of salty taste signalling mechanism’. He is Professor in the Faculty of Agriculture at Ryukoku University, Japan, with expertise in applied microbiology and biochemistry. Prior to this, he held positions at Japan’s Nara Women’s University, Kyoto University and Osaka Medical College, and Rockefeller University in the US. His current research surrounds the science behind the taste buds and has included projects such as ‘Food Components Inhibiting Recombinant Human Histidine Decarboxylase Activity’, ‘Construction of Free Amino Acids Composition Data Base for Food’, and general biochemical approaches including high pressure bioscience toward glutamate decarboxylase, histidine decarboxylase, miraculin and serine carboxypeptidase Y. He has a special interest in gamma amino butyric acid (GABA), which is the main inhibitory neurotransmitter in the mammalian central nervous system. It is produced from L-glutamic acid in the decarboxylation reaction catalysed by glutamic acid decarboxylase (GAD). GABA sends chemical messages through the brain and the nervous system and is involved in regulating communication between brain cells. Due to the expected physiological effect of GABA in the suppression of blood pressure increase, diuretic effect and relaxation effect, it is also being used in health food products. However, as the molecular role of GABA and GAD is not fully understood, Ueno and his team are seeking to unravel these molecular mysteries. In the team’s project, ‘Search for salt-enhancement materials from natural resources by using GABA-synthetic enzyme, development of low-salt content foods, and study of salt signal transduction mechanism’, the researchers began by exploring where GAD locates in the body. They used an immuno-histochemical method and identified the localisation of GAD65 and GAD67 in the stomach, intestine and skin. However, due to the limitations associated with this method, the team was unable to identify further locations. Later, when the team used a GAD67/GFP knock-in mouse, the researchers were able to identify GAD67 localisation on type III taste buds, which are known to express salt and acid receptors, while the GABA receptor is known as the chloride ion channel and to participate in salt sensation. Ueno provides an insight into the relationship between GABA and taste: ‘In the field of cookery, it is known that a small amount of salt enhances sweetness as well as umami. This effect is called ‘contrast effect’. If you control GABA levels in the cell, it should affect umami taste.