Isocitrate dehydrogenase and isocitrate lyase are essential enzymes for riboflavin production in Ashbya gossypii

For this study, we hypothesized that mitochondrial NAD(+)-dependent isocitrate dehydrogenase 1 (ICDH1) and isocitrate lyase (ICL1) were important enzymes for riboflavin synthesis in the fungus Ashbya gossypii. Here, the genes encoding ICDH1 and ICL1 were disrupted in order to analyze the enzymes' functions on riboflavin production by the fungus. The riboflavin production resulting from these disruptants was markedly decreased compared to the concentration produced by its parental strain when cultured in a rich nutrient medium used to optimize riboflavin production. Furthermore, when comparing the transcription levels of the genes encoding ICDH1 and ICL1, between wild-type A. gossypii and an itaconate resistant mutant of A. gossypii obtained by UV irradiation, the mRNA levels in the mutant were 1.8- and 2.0-fold higher than those in the wild-type strain, respectively. These results indicate that ICDH1 and ICL1 are key enzymes for riboflavin synthesis in A. gossypii. (c) KSBB.