Biosynthesis mechanism of ‘isoallysin’, the spicy onion flavor, revealed

The Rural Development Administration (RDA, Administrator Kwon Jae-han) conducted a study on the biosynthesis of isoallicin, the spicy component of onions, and discovered for the first time in the world that isoallicin is a unique defense system of onions against biological stress.

 Onions are an important vegetable crop consumed worldwide. Isoallysin in onions has a unique spicy taste and aroma, and is known to have various pharmacological effects due to its strong antioxidant action.

 It has been known that onion isoallysin is produced when onion cells are damaged and the enzyme alliinase stored in the vacuoles ^{* is released to break down isoalin in the cytoplasm.}

 * Vacuole: an organelle within a cell filled with water containing inorganic or organic molecules.

 However, the research team discovered the allinase enzyme present in the cytoplasm for the first time in the world through this study and revealed that isoallysin can be produced without damaging onion cells.

 If the alliinase enzyme is present in the cytoplasm, it can react directly with iso-allyl, so iso-allylcin can be produced without damaging the onion cells. The substance that causes tears to flow when cutting onions, lachrymatory factor (LF), is also produced during this process.

 This means that isoallysin and LF are produced and secreted even when onion cells are not damaged, and that these substances are used to block external invaders while the onion grows.

 In fact, in Asia, including Korea, intercropping and mixing vegetable crops with onions, green onions, and garlic has been practiced for a long time, and many studies have reported that this type of farming method reduces damage to crops from pathogens and pests. This study provides scientific evidence for this.

 The results of this study were published in a paper in Frontiers in Plant Science (IF 5.6), and are expected to be used as basic data on the biochemical defense system of onions for the development of eco-friendly agricultural technologies and disease-resistant varieties.

 According to Kwon Soo-jin, head of the Genome Division at the Rural Development Administration, “This study has allowed us to understand not only the isoallysin biosynthetic mechanism in onions, but also the defense system of Allium crops such as green onions and garlic.” He continued, “Based on this, we may be able to identify the correlation between isoallysin and the storability of onions, which may help reduce the spoilage rate of stored onions.”

Editor. Hong Se-yeong