Transcriptional regulation of the aceBAK and the glc operon. (A): the aceBAK operon. Genes encode for the following enzymes; aceB: malate synthase A, aceA: isocitrate lyase, aceK: isocitrate dehydrogenase kinase/phosphatase. IclR and ArcA are repressors, FruR and IHF activate transcription . The role of Crp is somewhat unclear. It has been reported as a repressor [25, 39], but metabolic flux analysis and enzyme activity measurements show its role as an activator [23, 83]. (B): the glc operons. Genes encode for the following enzymes; glcC: glycolate DNA binding regulator, glcDEF: glycolate oxidase subunits, glcG: conserved protein with unknown function, glcB: malate synthase G, glcA: glycolate transporter. ArcA and Fis are transcriptional repressors, Crp and IHF are activators. GlgC (glucose-1-phosphate adenylyltransferase, active in glycogen biosynthesis) activates the glcD operon and represses the glcC operon .