In 1987,a novel fibrinolytic enzyme (nattokinase) was discovered from a typical and popular fermented Japanese soybean food called natto [1].Since then,several fibrinolytic enzymes have been discovered in traditional foods,such as douche,brewing rice wine,tempeh,chungkookjang,salty fermented fish,and fermented shrimp paste [2,3].Due to the prevalence of nattokinase as a health food especially in Asia,numerous biochemical studies have been carried out to characterize this enzyme.It was found that nattokinase is a highly conserved serine protease which is a very effective extracellular enzyme composed of 275 amino acids [4].The nattokinase shows higher enzymatic activity than plasmin with direct fibrinolytic properties both in vitro and in vivo [5].Most of the proteases derived from the Bacillus subtilis are highly conserved.Alignment of 28 nattokinase sequences retrieved from the current NCBI Protein Search Database showed that they shared more than 90％ sequence identity.For example,three mature peptides from B.subtilis,nattokinase (GenBank no.AHZ12722.1),nattokinase (GenBank no.ABA29609.1),and nattokinase (GenBank no.ABM97611.1) shared 93％ sequence identity (Supplementary Fig.S1).