Yet another gift from Bacillus subtilis found inside natto is a medicinal enzyme called "nattokinase". This protein is made by the bacteria during fermentation of natto and is not found in other soy-based foods (1). Nattokinase is commonly taken as a drug/supplement blood thinner or blood clotting inhibitor as an alternative therapy for cardiovascular disease and stroke prevention (2).
Nattokinase (for biogeeks, despite its name) is a proteolytic enzyme (serine protease), meaning it functions in breaking down proteins (3). All proteins are made of chains of amino acids, precisely ordered in a genetically programmed sequence. Serine proteases (which themselves are also proteins) are designed to recognize and disassemble certain kinds of target proteins by cleaving them within a particular set sequence of amino acids (containing a serine residue) (4). Nattokinase has been found to target and break down target human proteins involved in blood clotting; thus acting as a natural inhibitor of blood clot formation or "blood thinner".
Incredibly, nattokinase's potential usefulness doesn't stop there. Many scientists from around the world have also seen that nattokinase may also be effective at inhibiting more kinds of unwanted protein aggregations (in addition to blot clot formation) within the human body. For example, Alzheimer's disease is well known to be associated with the abnormal accumulation of amyloid protein fibers and plaques in the brain. Nattokinase has been shown to be capable of breaking down these amyloid fibrils! (5)
Nattokinase is actually being studied as a potential drug therapy for multiple human amyloid disorders involving pathogenic protein fiber formation including: Alzheimer's (beta-amyloid fibrils), diabetes (insulin fibers) and prion diseases (prion peptide polymers) (2).
Nattokinase enzyme can be extracted from natto or now made by bacteria alone, and is commonly sold in pill form as shown above at Whole Foods. It's not cheap and, like probiotic supplements, it's unlikely that this shelf-stable, isolated form of nattokinase is as active as the protein coming from live Bacillus in natto food. Why, oh why not just eat fresh, delicious, nutritious and less expensive natto?
References: (1) Fujita, M.; Nomura, K.; Hong, K.; Ito, Y.; Asada, A.; Nishimuro, S. (1993). "Purification and Characterization of a Strong Fibrinolytic Enzyme (Nattokinase) in the Vegetable Cheese Natto, a Popular Soybean Fermented Food in Japan". Biochemical and Biophysical Research Communications 197 (3): 1340–1347. doi:10.1006/bbrc.1993.2624. PMID (2) Wikipedia [Nattokinase] https://en.wikipedia.org/wiki/Nattokinase (3) Wikipedia [serine protease]: https://en.wikipedia.org/wiki/Serine_protease (4) Yanagisawa, Y.; Chatake, T.; Chiba-Kamoshida, K.; Naito, S.; Ohsugi, T.; Sumi, H.; Yasuda, I.; Morimoto, Y. (2010). "Purification, crystallization and preliminary X-ray diffraction experiment of nattokinase fromBacillus subtilis natto". Acta Crystallographica Section F Structural Biology and Crystallization Communications 66 (12): 1670–1673. (5) Hs,u R.L. et al. (2009).Amyloid-degrading ability of nattokinase from Bacillus subtilis natto. J Agric Food Chem. 2009 Jan 28;57(2):503-8. doi: 10.1021/jf803072r.