A PRESUMABLE PATHWAY OF KOJIC ACID FORMATION FROM FRUCTOSE BY GLUCONOEACTER

Abstract

1. The unknown substance reported in the previous paper was identified as glucosone. The formation of glucosone from fructose by Gluconoacetobacter roseus is a similar reaction with the formation of reductone (enol form of glycerosone) from dihydroxyacetone by the same bacterium. A presumable pathway of ketose oxidation would be shown as follows:
2. The fructose dehydrogenase of G. roseus was investigated by Thunberg method. The activity of this dehydrogenase was the same order as that of gluconic acid dehydrogenase and was inhibited by the addition of 1:5.000mol. of 2, 4-dinitrophenol, when other dehydrogenases such as glucose, gluconic acid, and mannitol dehydrogenase were not affected. The fructose dehydrogenase of this bacterium seemed to be of the same type as the dihydroxyacetone dehydrogenase of Acetobacter suboxydans.
3. The author isolated a new substance from the fermented broth of fructose. The chemical structure of this compound is now under further investigation. This compound developes purple color with ferric chloride solution and gives different m.p. and R_f value from those of kojic acid, comenic acid, and rubiginol.
4. Although the biological induction of kojic acid from glucosone is not yet attained, the author assumes that glucosone would be the most possible intermediate of kojic acid formation, because Bond, Knight and Walker proved in 1937 the existance of the same substance in the brothh fermented by Aspergillus cryzae.