Comparative Analysis of Catabolic and Anabolic Dehydroshikimate Dehydratases for 3,4-DHBA Production in Escherichia coli

The production of 3,4-dihydroxybenzoic acid (3,4-DHBA or protocatechuate) is a relevant task owing to 3,4-DHBA’s pharmaceutical properties and its use as a precursor for subsequent synthesis of high value-added chemicals. The microbial production of 3,4-DHBA using dehydroshikimate dehydratase (DSD) (EC: 4.2.1.118) has been demonstrated previously. DSDs from soil-dwelling organisms (where DSD is involved in quinate/shikimate degradation) and from Bacillus spp. (synthesizing the 3,4-DHBA-containing siderophore) were compared in terms of the kinetic properties and their ability to produce 3,4-DHBA. Catabolic DSDs from Corynebacterium glutamicum (QsuB) and Neurospora crassa (Qa-4) had higher K(m) (1 and 0.6 mM, respectively) and k(cat) (61 and 220 s(−1), respectively) than biosynthetic AsbF from Bacillus thuringiensis (K(m)~0.04 mM, k(cat)~1 s(−1)). Product inhibition was found to be a crucial factor when choosing DSD for strain development. AsbF was more inhibited by 3,4-DHBA (IC(50)~0.08 mM), and Escherichia coli MG1655 ΔaroE P(lacUV5)-asbF(attφ80) strain provided only 0.2 g/L 3,4-DHBA in test-tube fermentation. Isogenic strains MG1655 ΔaroE P(lacUV5)-qsuB(attφ80) and MG1655 ΔaroE P(lacUV5)-qa-4(attφ80) expressing QsuB and Qa-4 with IC(50) ~0.35 mM and ~0.64 mM, respectively, accumulated 2.7 g/L 3,4-DHBA under the same conditions.