Histidine biosynthesis, its regulation and biotechnological application in C orynebacterium glutamicum

Summary l ‐Histidine biosynthesis is an ancient metabolic pathway present in bacteria, archaea, lower eukaryotes, and plants. For decades l ‐histidine biosynthesis has been studied mainly in E scherichia coli and S almonella typhimurium , revealing fundamental regulatory processes in bacteria. Furthermore, in the last 15 years this pathway has been also investigated intensively in the industrial amino acid‐producing bacterium C orynebacterium glutamicum , revealing similarities to E . coli and S . typhimurium , as well as differences. This review summarizes the current knowledge of l ‐histidine biosynthesis in C . glutamicum . The genes involved and corresponding enzymes are described, in particular focusing on the imidazoleglycerol‐phosphate synthase ( HisFH ) and the histidinol‐phosphate phosphatase ( HisN ). The transcriptional organization of his genes in C . glutamicum is also reported, including the four histidine operons and their promoters. Knowledge of transcriptional regulation during stringent response and by histidine itself is summarized and a translational regulation mechanism is discussed, as well as clues about a histidine transport system. Finally, we discuss the potential of using this knowledge to create or improve C . glutamicum strains for the industrial l ‐histidine production.