Biosynthetic pathway of 2,3-DHBA

In 1967 it was shown by Young et al. [84] that 2,3-DHBA in K. pneumoniae and E. coli is produced via the shikimic acid pathway (Fig. 1). Evidence showed that the centra) intermediate chorismic acid, leading to the aromatic amino acid pathways, is also the precursor for 2,3-DHBA. The formation of 2,3-DHBA required NAD, and Mg (Fig. 4) 

3-dihydro-2,3-DHBA yielding also an equimolar amount of pyruvate. The final step is the conversion to 2,3-DHBA in the presence of NAD [80,85,86]. 

Batterham and Gibson [87] firmly established isochorismate as an intermediate in 2,3-DHBA biosynthesis. Isochorismic acid is an unstable compound and at room temperature, in aqueous solution at pH 7, it decomposes readily to a mixture of SA and 

3-carboxyphenyl pyruvic acid [87]. Liu et al. [88] showed that the hydroxylgroup of 

3-DHBA is also an intermediate in the catabolism of L-tryptophan. 2,3-DHBA is formed in this pathway from anthranilate, by the enzyme anthranilate hydroxylase through deamination [89]. 

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