Biosynthetic pathway of SA

3-dihydro-2.3 dihydroxyber)zoic acid 2,3-dihydroxybenzoic acid 

Young et al. [80] postulated another possible pathway to SA, involving 2,3-dihydro- 

3-DHBA, followed by a dehydration. Such a pathway would require a co-factor as NAD, similar to the 2,3-DHBA biosynthesis. However, no evidence for such a NAD dependent conversion could be found in M smegmatis [77,78]. SA can also be obtained as an intermediate in naphthalene degradation [81]. 

The genes isolated from a pyoverdin mutant [82,83] showed two open reading frames (ORFs) pchB, encoding isochorismate pyruvate lyase, and pchA, encoding isochorismate synthase (Table 1) [79]. The TGA stopcodon of pchB overlaps the putative ATG startcodon of pchA and this suggests that these genes are in the same transcription unit. PchA is expressed only when pchB is transcribed and translated simultaneously. 

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Yalpani et al. [31] have shown conclusively that the biosynthetic pathway of SA in healthy and virus-inoculated tobacco (Nicotiana tabaccum) and tobacco cell-suspension cultures occurs via CA and BA. Unlabelled o-coumaric acid was detected after feeding with [ C]-CA. Moreover, it was shown that BA and not o-coumaric acid was incorporated in SA. 

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