Abstract
Ustilagic acid is a water-insoluble glycolipid produced by Ustilago may&, the corn smut fungus. It was discovered by Haskins (l), and its structure was elucidated by Lemieux, Thorn, and Bauer (2, 3). Pilot plant quantities are being produced in Japan.’ Ustilagic acid was shown to be a mixture of acylated derivatives of /I-n-cellobiosyl-15u, l&dihydroxy-n-hexadecanoic acid (glucoustilic acid A) and @-D-cellobiosyl-2n, 15~~ 16-trihydroxy-n-hexadecanoic acid (glucoustilic acid B). The major components (Fig. 1) of the mixture were considered to be diesters of the glucoustilic acids with acetic acid and either n-P-hydroxyn-hexanoic or L-P-hydroxy-n-octanoic acid. Minor components may contain n-hexanoyl groups. This work on the digestion of the complex, insoluble ustilagic acids was undertaken to determine the effect of acylation on the degradation of glycosides by fungi.
Highlights
F. moniliforme and related species are able to grow on it by virtue of an enzyme which catalyzes the hydrolysis of the glycosidic linkage
For want of a better name, the enzyme may be called “ustilagic acid hydrolase”, i.e. the glycosidase acting on ustilagic acid to produce diacyl cellobiose and ustilic acid
The susceptibility of the glycosidic linkage in ustilagic acid to hydrolysis by ustilagic acid hydrolase indicates a lack of interfering substituents on the potential reducing unit (Gl)
Summary
Chromatographic comparison of the samples, indicated that the four major components (A,, Az, Bi, 132) of the mixtures differed in relative amounts The 8038 ustilagic acid appeared to be predominantly A (Ai, As) ; the J II sample, predominantly B (Bi, Bt). 1.432 and [a]:’ +28” (c, 1.1% in CHCl,), was obtained through fractional distillation of a mixture of P-hydroxy acid esters derived from J II ustilagic acid by saponification and esterification with diazomethane (cf Lemieux [5]: b.p. 230” with decomposition at 710 mm; nz5 1.433; [oc], +24” (c, 0.85% in CHCl3). Since autoclaving results in clumping of ustilagic acid, sterilization of this substrate was accomplished by filtration of a 10%. The ustilagic acid was precipitated by addition of 4 volumes of sterile water, and the methanol was removed by centrifugation and further washing of the precipitate. P-hydroxy acid methyl esters on polydiethylene glycol succinate at 170” are: methyl n-decanoate, 1.00; methyl P-hydroxybutyrate, 1.12; methyl P-hydroxy-n-hexanoate, 1.87; and methyl phydroxy-n-octanoate, 3.62
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