If biotin is lacking, multiple carboxylase deficiencies arise [1] because biotin is a cofactor of the biotin-dependent carboxylases, which occur in all domains of life [2]. Many bacteria can synthesize biotin, but biotin auxotrophic bacteria such as Corynebacterium glutamicum require uptake of biotin from the habitat. Biotin synthesis can be subdivided into synthesis of pimelic acid followed by the biotin ring assembly [3]. Biotin
ring assembly occurs via the well-studied enzymes 8-amino-7-oxononanoate synthase, 7,see more 8-diaminononanoate synthase, dethiobiotin synthase and biotin Avapritinib in vitro synthase encoded by bioF, bioA, bioD and bioB, respectively [2]. Pimelate synthesis occurs via two alternative routes as found in Bacillus subtilis and Escherichia coli, respectively [3]. In B. subtilis, pimeloyl-CoA is generated by interception of fatty acid biosynthesis by P450-dependent BioI, which yields pimeloyl-ACP chains by oxidative cleavage of long-chain acyl-ACPs [4]. In E. coli, malonyl-CoA methyl ester is generated by SAM-dependent methyltransferase BioC as a primer molecule and afterwards elongated in fatty acid biosynthesis to yield methyl-pimeloyl-ACP which finally is demethylated by carboxylesterase BioH [5]. Other sources of pimeloyl-CoA are externally added pimelic acid which is activated by pimeloyl-CoA synthetase as e.g. in B. subtilis, yet uncharacterized
biosynthetic pathways as proposed e.g. for Desulfovibrio species [6] or degradation of benzene as e.g. in Rhodopseudomonas palustris [7]. C. glutamicum is a Gram-positive biotin-auxotrophic bacterium that was originally selleck chemical isolated as an L-glutamate producer from soil samples [8]. C. glutamicum lacks the ability to synthesize pimeloyl-CoA, but the enzymes for biotin ring assembly, BioA, BioD and BioB, are functional [9–11]. It has been proposed that biotin auxotrophy in C. glutamicum is due to the lack of a BioF homolog [9–11]. Accordingly, it has been found that biotin, dethiobiotin, and aminopelargonic acid derivatives effectively
support growth when added in low concentrations, but not pimelic acid [12]. Biotin auxotrophy of C. glutamicum elicits L-glutamate production, a characteristic which led to its discovery. L-Glutamate production by C. glutamicum Glycogen branching enzyme can be triggered in number of alternative ways, e.g. by addition of ethambutol [13] or Tween [14] or by a temperature shift [15]. Triggering L-glutamate production by biotin limitation alters synthesis of fatty acids and mycolic acids [16] as a consequence of reduced activity of acyl-CoA carboxylases, which contain AccBC, one of the two biotin-containing enzymes of C. glutamicum [17] as α-subunit. Secretion of L-glutamate is mediated by a carrier [18, 19] involving the gene product of cg1434 [20], which encodes mechanosensitive channel MscS [21, 22]. Activation of MscS without osmotic downshock is thought to result in L-glutamate secretion [20–22].