Activation of Fibrinolysis (Nattokinase) Induced by Dipicolinic Acid and Related Compounds

Abstract

Culture medium containing dipicolinic acid at final concentrations of 0, 1, 2 and 4mM were inoculated with the Miyagino strain of Bacillus subtilis natto, the bacteria used for the production of natto, and subjected to stationary culture for 24 hours, after which the activity of nattokinase was investigated using two methods : a standard fibrin plate method, and the synthetic substrate Suc-Ala-Ala-Pro-Phe-pNA. Using the standard fibrin plate method, it was confirmed that nattokinase activity rose to 12.5FU/ml in the samples containing 2mM dipicolinic acid, a value 5.6 times greater than that of the sample containing no dipicolinic acid (2.25FU/ml). Colorimetric measurements using the synthetic substrate showed that the activity level was highest (168.5nmol/min/ml) with addition of 2mM dipicolinic acid, about 4.3 times the activity of the sample with no dipicolinic acid (39.6nmol/min/ml). The effects of dipicolinic acid were also clear for the Naruse strain of Bacillus subtilis natto. Based on the results of comparison tests using DPA and nine structurally related compounds, including nicotinic acid, it appears that dipicolinic acid is capable of enhancing specific nattokinase production to a considerable extent.