Abstract
(1) Piricularia oryzae is able to utilize DL-isoleucine as a carbon source through its conversion to α-keto analogue, i.e., α-keto-β-methylvaleric acid. This keto acid is identified as its. 2, 4-dinitrophenylhydrazone (racemic mixture).
(2). In, the incubation of Piricularia oryzae in the medium supplemented with DL-α-aminobutyric acid, the identification of α-ketobutyric acid was unsuccessful, but the formation of α-keto-β-methylvaleric acid was recognized by the separation of its 2, 4-dinitrophenylhydrazone (racemic mixture). This fact presents direct evidence supporting the nutritional significance of aminobutyric acid as an intermediate in the biosynthetic pathway of isoleucine, in addition to the suggestive prevalency of such biosynthetic route, at least, in microorganisms.
(3) The close metabolic relationship between isoleucine and α-aminobutyric acid is suggested by the separation and identification of pyruvic acid, α-ketoglutaric acid and α-keto-β-methylvaleric acid as 2, 4-dinitrophenyl-hydrazone in either incubation added with isoleucine or α-aminobutyric acid in the presence of arsenite.
(4) The availability of formate to this fungus is indicated.
(5) The possible mechanism of the formation of these three keto acids is discussed, taking into account the paper chromato-graphic evidence obtained with the culture medium.
