1965 Volume 30 Issue 3 Pages 139-144
Some compounds, which have an inhibitory effect on starch decomposition, are produced in the culture filtrate of Cochliobolus miyabeanus, the causal fungus of Helminthosporium leaf spot of rice plants. In this paper results on physico-chemical natures of the compounds were described.
1. These compounds are thermostable, and can not be extracted with ethylether, nor precipitated with 90 percent ethanol. They do not form chelate compounds with EDTA or citric acid, but are adsorbed with cation exchange resins. From these facts, it is evident that they are cations of low molecular weight, being neither protein, organic acid nor heavy metal. Consequently, they seem not to be any kinds of SH-inhibitors.
2. These compounds have only one peak of absorption spectrum at 310mμ.
3. These compounds have no relation with a brown color substance produced in the culture filtrate.
4. From the above results, it is assumed that the starch-decomposition-inhibiting substaces are some alkaline metabolites produced by the causal fungus, and that they are diffused from diseased lesions and inhibit β-amylase activity in the surrounding healthy tissues.