Comparative Analysis of Catabolic and Anabolic Dehydroshikimate Dehydratases for 3,4-DHBA Production in Escherichia coli
Ekaterina A. Shmonova; Ekaterina A. Savrasova; Elizaveta N. Fedorova; Vera G. Doroshenko
The production of 3,4-dihydroxybenzoic acid (3,4-DHBA or protocatechuate) is a relevant task owing to 3,4-DHBA&rsquo: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 Km (1 and 0.6 mM, respectively) and kcat (61 and 220 s&minus:1, respectively) than biosynthetic AsbF from Bacillus thuringiensis (Km~0.04 mM, kcat~1 s&minus:1). Product inhibition was found to be a crucial factor when choosing DSD for strain development. AsbF was more inhibited by 3,4-DHBA (IC50~0.08 mM), and Escherichia coli MG1655 &Delta:aroE PlacUV5-asbFatt&phi:80 strain provided only 0.2 g/L 3,4-DHBA in test-tube fermentation. Isogenic strains MG1655 &Delta:aroE PlacUV5-qsuBatt&phi:80 and MG1655 &Delta:aroE PlacUV5-qa-4att&phi:80 expressing QsuB and Qa-4 with IC50 ~0.35 mM and ~0.64 mM, respectively, accumulated 2.7 g/L 3,4-DHBA under the same conditions.
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