The biosynthesis of kojic acid. 1. Production from [1-14C] and [3:4-14C2]glucose and [2-14C]-1:3-dihydroxyacetone

Abstract

The conversion of glucose to kojic acid by two spp. of Aspergilli was studied using both [1-C14] and 3:4-Cl42] glucose. Between 70 and 90% of the total radioactivity of the isolated kojic acid was found in the C atoms corresponding to those labelled in the glucose, indicating that the major pathway of kojic acid formation is a direct conversion of glucose without splitting of the carbon chain. Symmetrical C3 or C6 compounds are not intermediates in the biosynthesis. A minor pathway of kojic acid biosynthesis, involving condensation of "small" molecules, probably triosephosphates, leads to incorporation of Cl4 into position 6 of kojic acid, when [1-Cl4]-glucose is used as substrate. The biosynthesis of kojic acid from [2-Cl4]-dihydroxyacetone, alone or in the presence of unlabelled glucose, was also studied. In the latter case, CH is incorporated predominantly into position 5 of kojic acid. Possible mechanisms for the conversion of glucose and dihydroxyacetone to kojic acid are discussed.