Enzymes relevant to kojic acid biosynthesis in Aspergillus flavus

Biochemistry Division, National Sugar Institute, Kanpur 208017, India ABSTRACT Hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glucose dehydrogenase, glucose oxidase and gluconate dehydrogenase have been demonstrated in mycelial homogenates from a strain of Aspergillus flavus that produces considerable amounts of kojic acid. The enzymes were assayed after different periods of growth under different experimental conditions and their activities were compared with the rate of kojic acid production. Glucose oxidase activity was too low to account for the formation of kojic acid but the other enzymes had sufficient activities. Correlation of the pattern of enzyme activities under different experimental conditions with kojic acid concentrations provided evidence for the involvement of glucose dehydrogenase and gluconate dehydrogenase in kojic acid biosynthesis. Based on these data a possible pathway for the biosynthesis of kojic acid is presented. Gluconic acid- -lactone and at least one of the three compounds, 3-ketogluconic acid lactone, 3-ketoglucose and oxykojic acid, are believed to be intermediates in this pathway. Present address: Department of Biochemical Engineering. Faculty of Engineering and Science, University of Western Ontario, London, Canada N6A 5B9.