Glycolic Acid Oxidase in Castor Bean Endosperm

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Abstract
Glycolic acid oxidase was present in endosperm tissue from germinating castor beans. Glycolic and lactic acid were oxidized to glyoxylic and pyruvic acids respectively. FMN and FAD stimulated the reaction. Twenty percent of the total activity was associated with the mito-chondrial fraction. The enzyme activity increased during germination, but the change in activity was not correlated with the glycolic acid content of the tissue. [alpha]-Hydroxy-2-pyridinemethanesulfonic acid and glyoxylate bisulfite, inhibitors of glycolic oxidase, curtailed respiration severely, but it was shown that their action is not exclusive to this enzyme. Inhibition of the respiration by cyanide was an additional consideration against the participation of glycolic oxidase as a terminal oxidase in endosperm tissue. Glycolate-1-C14 was metabolized by endosperm slices and evidently oxidized to glyoxylate. C14 appeared in the organic acid fraction, amino acids (principally serine and glycine), CO2, and, to a small extent, in the sugar fraction. The results are discussed in relation to the utilization of acetate, and it is concluded that the glycolate pathway does not contribute to sugar synthesis in the endosperm. The significance of glycolic oxidase in the tissue was not established.