Nattokinase is an enzyme derived from ""natto,"" a traditional fermented soy food popular in Japan. During the natto production process, non-gmo soybeans are boiled and fermented with friendly Bacillus subtilis bacteria producing nattokinase. Doctor's Best Nattokinase contains nattokinase enzyme with Vitamin K2 removed. Nattokinase has been shown to support the circulatory system by helping to maintain normal fibrinogen levels in blood.