D critically and compared with the information of histidine biosynthesis in Escherichia coli and Salmonella enterica serovar Typhimurium (S. typhimurium), the reference organisms concerning this particular pathway. Properties of L-histidineL-Histidine is one of the 20 common proteinogenic amino acids present in proteins of all living organisms. Inside the following, we will use the term histidine instead, which means its biologically active isomer L-histidine. Its side-chain is definitely an imidazole ring and thus has aromatic properties. Histidine would be the only amino acid whose side-chain can switch from an unprotonated to a protonated state beneath neutral pH circumstances on account of the pKa worth of 6.0 of its side-chain (Nelson and Cox, 2009). This characteristic IL-34 Protein site enables histidine residues to act as each, a proton acceptor or even a proton donor, in lots of cellular enzymatic reactions (Rebek, 1990; Polg , 2005).Received 21 December, 2012; revised 1 March, 2013; accepted five March, 2013. For correspondence. E-mail joern.kalinowski@ cebitec.uni-bielefeld.de; Tel. +49-(0)521-106-8756; Fax +49-(0)521106-89041. Microbial Biotechnology (2014) 7(1), five?five doi:10.1111/1751-7915.12055 Funding Data R. K. Kulis-Horn is supported by a CLIB-GC (Graduate Cluster Industrial Biotechnology) Phd grant co-funded by the Ministry of Innovation, Science and Research of the federal state of North Rhine-Westphalia (MIWF). This operate was element of your SysEnCor investigation project (Grant 0315598E) funded by the German Federal Ministry of Education and Analysis (BMBF).?2013 The Authors. Microbial Biotechnology published by John Wiley Sons Ltd and Society for Applied Microbiology. That is an open access article beneath the terms with the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, supplied the original work is properly cited.6 R. K. Kulis-Horn, M. Persicke and J. Kalinowski The histidine biosynthesis pathway Because the late 1950s, the histidine biosynthesis pathway has been DKK1 Protein Formulation studied intensively in various organisms like yeasts, S. typhimurium, and E. coli. Initially, Ames and Martin elucidated the comprehensive histidine pathway by identifying all metabolic intermediates and also the enzymes catalysing the corresponding reactions in S. typhimurium (Brenner and Ames, 1971; Martin et al., 1971). At that time, final uncertainties remained with regards to the reaction measures and intermediates in the interconnection towards the pathway of de novo purine biosynthesis. These challenges have been finally elucidated by Klem and Davisson revealing the final variety of catalytic reactions and intermediates (Klem and Davisson, 1993). Based on this understanding, histidine biosynthesis is an unbranched pathway with ten enzymatic reactions, starting with phosphoribosyl pyrophosphate (PRPP) and major to L-histidine (Fig. 1) (Alifano et al., 1996; Stepansky and Leustek, 2006). It turned out early that the histidine pathways of S. typhimurium and E. coli are identical. Additionally, histidine biosynthesis seems to be conserved in all organisms such as archaea (Lee et al., 2008), Gram-positive bacteria (Chapman and Nester, 1969), decrease eukaryotes (Fink, 1964), and plants (Stepansky and Leustek, 2006). The common histidine pathway and its regulation has already been reviewed in excellent detail, mainly focusing on E. coli, S. typhimurium, and plants (Brenner and Ames, 1971; Martin et al., 1971; Alifano et al., 1996; Winkler, 1996; Stepansky and Leustek, 2006). This work focuses around the histidine bi.