Nattokinase (pronounced ) is an enzyme extracted and purified from a Japanese food called nattō. Nattō is produced by fermentation by adding the bacterium Bacillus subtilis var natto, which also produces the enzyme, to boiled soybeans. While other soy foods contain enzymes, it is only the nattō preparation that contains the specific nattokinase enzyme under the Japan Nattokinase Administration and Ministry of Health, Labour and Welfare. In spite of its name, nattokinase is not a kinase enzyme (and should not be pronounced as such), but a serine protease of the subtilisin family (99.5% identical with aprE). Rather, it is named for the fact that it is an enzyme produced by nattōkin (納豆菌), the Japanese name for Bacillus subtilis var natto. When in contact with human blood or blood clots, it exhibits a strong fibrinolytic activity and works by inactivating plasminogen activator inhibitor 1 (PAI-1). Although it should be expected to be digested and inactivated in the human gut like other proteins, a few researchers report that nattokinase is active even when taken orally and consumed. Nattokinase can also be sold as a dietary supplement. It can now be produced by recombinant means and in batch culture, rather than relying on extraction from nattō or eating it whole.