| Research Abstract |
An analysis of dipicolinic acid (DPA,2,6-pyridinedicarboxylic acid) contained in Bacillus subtilis natto cells using the colorimetric method of Janssen and others showed that the largest DPA content is approximately 2.4-3.6% of the total dry weight.
A comparison of the antibacterial activity of DPA and its derivatives-quinolic acid (2,3-pyridine dicarboxylic acid), 2,4-pyridine dicarboxylic acid, isoinchlorendic acid (2,5-pyridine dicarboxylic acid), and 3,5-pyridine dicarboxylic acid-revealed that this antibacterial activity is unique to DPA. Moreover, an investigation into the effects of various metal ions on the antibacterial activity showed that the activity is strongly inhibited through the addition of Ca^<++>,Fe^<++>,Co^<++>, and Zn^<++>, all divalent ions.
It was also shown that the addition of DPA increases the amount of nattokinase produced by Bacillus subtilis natto. In four types of Bacillus subtilis natto, the Miyagino, Meguro, Takahashi and Naruse types, DPA with a 2 mM conc
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entration increased the amount of nattokinase produced. In the case of the Miyagino type, for example, the fibrinolytic activity for fibrin plates was double the level seen for the sample with no DPA added, at 256.1 mm^2/30 μl at 37℃ after four hours (1,500 FU/ml for the nattokinase activity). A comparison test, with 10 types of nicotinic acid-related substances added, showed that dipicolinic acid had the strongest effect.
DPA with a final concentration of 5×10^<-3> mol/l was found to substantially inhibit the platelet aggregation reaction caused by human adenosine triphosphate(ATP), as well as the reaction of thrombin converting fibrinogen into fibrin. It became clear that at 5×10^<-3> mol/l, there was a complete inhibition of the blood coagulation reaction as observed in thromboelastography, while such strong effects were not observed in the case of DPA derivatives, even at 10 mM. There were no changes in human prothrombin time, the thromboplastin time for the active areas, or euglobulin lysis time.
Although platelet aggregation in human blood is observed with 30 μM of adenosine diphosphate(ADP), it became clear that dose-dependent inhibition of this aggregation occurs when there is 5×10^<-3> M of DPA. The calculated CI_<50> was at the fairly low concentration of 1.8×10^<-3> M, and far stronger (4.0×10^<-2> M) than in the case of adding aspirin for clinical use. Less
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